Binuclear metal complexes for use as emitters in organic electroluminescent devices

ABSTRACT

The present invention relates to binuclear metal complexes and electronic devices, in particular organic electroluminescent devices containing said metal complexes.

This application is a national stage entry, filed pursuant to 35 U.S.C. § 371, of PCUEP2017/073385, filed Sep. 18, 2017, which claims the benefit of European Patent Application No. 16189816.8, filed Sep. 21, 2016, which is incorporated herein by reference in its entirety.

The present invention relates to binuclear metal complexes suitable for use as emitters in organic electroluminescent devices.

According to the prior art, triplet emitters used in phosphorescent organic electroluminescent devices (OLEDs) are, in particular, bis- and tris-ortho-metalated iridium complexes having aromatic ligands, where the ligands bind to the metal via a negatively charged carbon atom and an uncharged nitrogen atom or via a negatively charged carbon atom and an uncharged carbene carbon atom. Examples of such complexes are tris(phenylpyridyl)iridium(III) and derivatives thereof, where the ligands used are, for example, 1- or 3-phenylisoquinolines, 2-phenylquinolines or phenylcarbenes. In this case, these iridium complexes generally have quite a long luminescence lifetime in the region of well above 1 μs. For use in OLEDs, however, short luminescence lifetimes are desired in order to be able to operate the OLED at high brightness with low roll-off characteristics. There is still need for improvement in efficiency of red-phosphorescing emitters as well. As a result of the low triplet level T₁ in the case of customary red-phosphorescing emitters, the photoluminescence quantum yield is frequently well below the value theoretically possible since, with low T₁, non-radiative channels also play a greater role, especially when the complex has a high luminescence lifetime. An improvement by increasing the radiative levels is desirable here, which can in turn be achieved by a reduction in the photoluminescence lifetime.

An improvement in the stability of the complexes was achieved by the use of polypodal ligands, as described, for example, in WO 2004/081017, U.S. Pat. No. 7,332,232 and WO 2016/124304. Even though these complexes show advantages over complexes which otherwise have the same ligand structure except that the individual ligands therein do not have polypodal bridging, there is still a need for improvement. Thus, in the case of complexes having polypodal ligands too, improvements are still desirable in relation to the properties on use in an organic electroluminescent device, especially in relation to luminescence lifetime of the excited state, efficiency, voltage and/or lifetime.

US 2003/0152802 discloses bimetallic iridium complexes having a bridging ligand that coordinates to both metals. These complexes are synthesized in multiple stages, which constitutes a synthetic disadvantage. Moreover, facial-meridional isomerization and ligand scrambling are possible in these complexes, which is likewise disadvantageous.

It is therefore an object of the present invention to provide novel metal complexes suitable as emitters for use in OLEDs. It is a particular object to provide emitters which exhibit improved properties in relation to luminescence lifetime, efficiency, operating voltage and/or lifetime.

It has been found that, surprisingly, the binuclear rhodium and iridium complexes described below show distinct improvements in photophysical properties compared to corresponding mononuclear complexes and hence also lead to improved properties when used in an organic electroluminescent device. More particularly, the compounds of the invention have an improved photoluminescence quantum yield and a distinctly reduced luminescence lifetime. A shorter luminescence lifetime leads to improved roll-off characteristics of the organic electroluminescent device. The present invention provides these complexes and organic electroluminescent devices comprising these complexes.

The invention thus provides a compound of the following formula (1):

-   where the symbols used are as follows: -   M is the same or different at each instance and is iridium or     rhodium; -   D is the same or different at each instance and is C or N; -   X is the same or different at each instance and is CR or N; or two     adjacent X together are CR or N and the third X is CR or N when     either one D in this cycle coordinates as an anionic nitrogen atom     to M or when E is N; -   E is C or N, where E can only be N when two adjacent X together are     CR or N and the third X is CR or N; -   V is the same or different at each instance and is a group of the     following formula (2) or (3):

-   -   where the dotted bond bonded directly to the cycle represents         the bond to the corresponding 6-membered aryl or heteroaryl         group shown in formula (1) and the two dotted bonds to A each         represent the bonds to the sub-ligands L;

-   L is the same or different at each instance and is a bidentate     monoanionic sub-ligand;

-   X¹ is the same or different at each instance and is CR or N;

-   X² is the same or different at each instance and is CR or N or two     adjacent X² groups together are NR, O or S, thus forming a     five-membered ring, and the remaining X² are the same or different     at each instance and are CR or N; or two adjacent X² groups together     are CR or N when one of the X³ groups in the cycle is N, thus     forming a five-membered ring; with the proviso that not more than     two adjacent X² groups are N;

-   X³ is C at each instance or one X³ group is N and the other X³     groups in the same cycle are C; with the proviso that two adjacent     X² groups together are CR or N when one of the X³ groups in the     cycle is N;

-   A¹ is the same or different at each instance and is C(R)₂ or O;

-   A² is the same or different at each instance and is CR, P(═O), B or     SiR, with the proviso that, when A²=P(═O), B or SiR, the symbol A¹     is O and the symbol A bonded to this A² is not —C(═O)—NR′— or     —C(═O)—O—;

-   A is the same or different at each instance and is —CR═CR—,     —C(═O)—NR′—, —C(═O)—O—, —CR₂—CR₂—, —CR₂—O— or a group of the     following formula (4):

-   -   where the dotted bond represents the position of the bond of a         bidentate sub-ligand L to this structure and * represents the         position of the linkage of the unit of the formula (4) to the         central cyclic group, i.e. the group shown explicitly in         formula (2) or (3), and X² and X³ have the definitions given         above;

-   R is the same or different at each instance and is H, D, F, Cl, Br,     I, N(R¹)₂, CN, NO₂, OR¹, SR¹, COOH, C(═O)N(R¹)₂, Si(R¹)₃, B(OR¹)₂,     C(═O)R¹, P(═O)(R¹)₂, S(═O)R¹, S(═O)₂R¹, OSO₂R¹, COO(cation),     SO₃(cation), OSO₃(cation), OPO₃(cation)₂, O(cation), N(R¹)₃(anion),     P(R¹)₃(anion), a straight-chain alkyl group having 1 to 20 carbon     atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms or     a branched or cyclic alkyl group having 3 to 20 carbon atoms, where     the alkyl, alkenyl or alkynyl group may in each case be substituted     by one or more R¹ radicals, where one or more nonadjacent CH₂ groups     may be replaced by Si(R¹)₂, C═O, NR¹, O, S or CONR¹, or an aromatic     or heteroaromatic ring system which has 5 to 40 aromatic ring atoms     and may be substituted in each case by one or more R¹ radicals; at     the same time, two R radicals together may also form a ring system;

-   R′ is the same or different at each instance and is H, D, a     straight-chain alkyl group having 1 to 20 carbon atoms or a branched     or cyclic alkyl group having 3 to 20 carbon atoms, where the alkyl     group in each case may be substituted by one or more R¹ radicals and     where one or more nonadjacent CH₂ groups may be replaced by Si(R¹)₂,     or an aromatic or heteroaromatic ring system which has 5 to 40     aromatic ring atoms and may be substituted in each case by one or     more R¹ radicals;

-   R¹ is the same or different at each instance and is H, D, F, Cl, Br,     I, N(R²)₂, CN, NO₂, OR², SR², Si(R²)₃, B(OR²)₂, C(═O)R², P(═O)(R²)₂,     S(═O)R², S(═O)₂R², OSO₂R², COO(cation), SO₃(cation), OSO₃(cation),     OPO₃(cation)₂, O(cation), N(R²)₃(anion), P(R²)₃(anion), a     straight-chain alkyl group having 1 to 20 carbon atoms or an alkenyl     or alkynyl group having 2 to 20 carbon atoms or a branched or cyclic     alkyl group having 3 to 20 carbon atoms, where the alkyl, alkenyl or     alkynyl group may in each case be substituted by one or more R²     radicals, where one or more nonadjacent CH₂ groups may be replaced     by Si(R²)₂, C═O, NR², O, S or CONR², or an aromatic or     heteroaromatic ring system which has 5 to 40 aromatic ring atoms and     may be substituted in each case by one or more R² radicals; at the     same time, two or more R¹ radicals together may form a ring system;

-   R² is the same or different at each instance and is H, D, F or an     aliphatic, aromatic or heteroaromatic organic radical, especially a     hydrocarbyl radical, having 1 to 20 carbon atoms, in which one or     more hydrogen atoms may also be replaced by F;

-   cation is the same or different at each instance and is selected     from the group consisting of proton, deuteron, alkali metal ions,     alkaline earth metal ions, ammonium, tetraalkylammonium and     tetraalkylphosphonium;

-   anion is the same or different at each instance and is selected from     the group consisting of halides, carboxylates R₂—COO⁻, cyanide,     cyanate, isocyanate, thiocyanate, thioisocyanate, hydroxide, BF₄ ⁻,     PF₆ ⁻, B(C₆F₅)₄ ⁻, carbonate and sulfonates.

When two R or R¹ radicals together form a ring system, it may be mono- or polycyclic, and aliphatic, heteroaliphatic, aromatic or heteroaromatic. In this case, the radicals which together form a ring system may be adjacent, meaning that these radicals are bonded to the same carbon atom or to carbon atoms directly bonded to one another, or they may be further removed from one another, but are preferably adjacent.

The wording that two or more radicals together may form a ring, in the context of the present description, shall be understood to mean, inter alia, that the two radicals are joined to one another by a chemical bond with formal elimination of two hydrogen atoms. This is illustrated by the following scheme:

In addition, however, the abovementioned wording shall also be understood to mean that, if one of the two radicals is hydrogen, the second radical binds to the position to which the hydrogen atom was bonded, forming a ring. This shall be illustrated by the following scheme:

The formation of an aromatic ring system shall be illustrated by the following scheme:

This kind of ring formation is possible in radicals bonded to carbon atoms directly bonded to one another, or in radicals bonded to further-removed carbon atoms. Preference is given to this kind of ring formation in radicals bonded to carbon atoms directly bonded to one another or to the same carbon atom.

An aryl group in the context of this invention contains 6 to 40 carbon atoms; a heteroaryl group in the context of this invention contains 2 to 40 carbon atoms and at least one heteroatom, with the proviso that the sum total of carbon atoms and heteroatoms is at least 5. The heteroatoms are preferably selected from N, O and/or S. An aryl group or heteroaryl group is understood here to mean either a simple aromatic cycle, i.e. benzene, or a simple heteroaromatic cycle, for example pyridine, pyrimidine, thiophene, etc., or a fused aryl or heteroaryl group, for example naphthalene, anthracene, phenanthrene, quinoline, isoquinoline, etc.

An aromatic ring system in the context of this invention contains 6 to 40 carbon atoms in the ring system. A heteroaromatic ring system in the context of this invention contains 1 to 40 carbon atoms and at least one heteroatom in the ring system, with the proviso that the sum total of carbon atoms and heteroatoms is at least 5. The heteroatoms are preferably selected from N, O and/or S. An aromatic or heteroaromatic ring system in the context of this invention shall be understood to mean a system which does not necessarily contain only aryl or heteroaryl groups, but in which it is also possible for a plurality of aryl or heteroaryl groups to be interrupted by a nonaromatic unit (preferably less than 10% of the atoms other than H), for example a carbon, nitrogen or oxygen atom or a carbonyl group. For example, systems such as 9,9′-spirobifluorene, 9,9-diarylfluorene, triarylamine, diaryl ethers, stilbene, etc. shall thus also be regarded as aromatic ring systems in the context of this invention, and likewise systems in which two or more aryl groups are interrupted, for example, by a linear or cyclic alkyl group or by a silyl group. In addition, systems in which two or more aryl or heteroaryl groups are bonded directly to one another, for example biphenyl, terphenyl, quaterphenyl or bipyridine, shall likewise be regarded as an aromatic or heteroaromatic ring system. Preferred aromatic or heteroaromatic ring systems are aryl or heteroaryl groups, systems in which two or more aryl or heteroaryl groups are bonded directly to one another, and fluorene and spirobifluorene groups.

A cyclic alkyl group in the context of this invention is understood to mean a monocyclic, bicyclic or polycyclic group.

In the context of the present invention, a C₁- to C₂₀-alkyl group in which individual hydrogen atoms or CH₂ groups may also be replaced by the abovementioned groups is understood to mean, for example, the methyl, ethyl, n-propyl, i-propyl, cyclopropyl, n-butyl, i-butyl, s-butyl, t-butyl, cyclobutyl, 2-methylbutyl, n-pentyl, s-pentyl, t-pentyl, 2-pentyl, neopentyl, cyclopentyl, n-hexyl, s-hexyl, t-hexyl, 2-hexyl, 3-hexyl, neohexyl, cyclohexyl, 1-methylcyclopentyl, 2-methylpentyl, n-heptyl, 2-heptyl, 3-heptyl, 4-heptyl, cycloheptyl, 1-methylcyclohexyl, n-octyl, 2-ethylhexyl, cyclooctyl, 1-bicyclo[2.2.2]octyl, 2-bicyclo[2.2.2]octyl, 2-(2,6-dimethyl)octyl, 3-(3,7-dimethyl)octyl, adamantyl, trifluoromethyl, pentafluoroethyl, 2,2,2-trifluoroethyl, 1,1-dimethyl-n-hex-1-yl, 1,1-dimethyl-n-hept-1-yl, 1,1-dimethyl-n-oct-1-yl, 1,1-dimethyl-n-dec-1-yl, 1,1-dimethyl-n-dodec-1-yl, 1,1-dimethyl-n-tetradec-1-yl, 1,1-dimethyl-n-hexadec-1-yl, 1,1-dimethyl-n-octadec-1-yl, 1,1-diethyl-n-hex-1-yl, 1,1-diethyl-n-hept-1-yl, 1,1-diethyl-n-oct-1-yl, 1,1-diethyl-n-dec-1-yl, 1,1-diethyl-n-dodec-1-yl, 1,1-diethyl-n-tetradec-1-yl, 1,1-diethyl-n-hexadec-1-yl, 1,1-diethyl-n-octadec-1-yl, 1-(n-propyl)cyclohex-1-yl, 1-(n-butyl)cyclohex-1-yl, 1-(n-hexyl)cyclohex-1-yl, 1-(n-octyl)cyclohex-1-yl and 1-(n-decyl)cyclohex-1-yl radicals. An alkenyl group is understood to mean, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl or cyclooctadienyl. An alkynyl group is understood to mean, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl or octynyl. A C₁- to C₂₀-alkoxy group as present for OR¹ or OR² is understood to mean, for example, methoxy, trifluoromethoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy or 2-methylbutoxy.

An aromatic or heteroaromatic ring system which has 5-40 aromatic ring atoms and may also be substituted in each case by the abovementioned radicals and which may be joined to the aromatic or heteroaromatic system via any desired positions is understood to mean, for example, groups derived from benzene, naphthalene, anthracene, benzanthracene, phenanthrene, benzophenanthrene, pyrene, chrysene, perylene, fluoranthene, benzofluoranthene, naphthacene, pentacene, benzopyrene, biphenyl, biphenylene, terphenyl, terphenylene, fluorene, spirobifluorene, dihydrophenanthrene, dihydropyrene, tetrahydropyrene, cis- or trans-indenofluorene, cis- or trans-monobenzoindenofluorene, cis- or trans-dibenzoindenofluorene, truxene, isotruxene, spirotruxene, spiroisotruxene, furan, benzofuran, isobenzofuran, dibenzofuran, thiophene, benzothiophene, isobenzothiophene, dibenzothiophene, pyrrole, indole, isoindole, carbazole, indolocarbazole, indenocarbazole, pyridine, quinoline, isoquinoline, acridine, phenanthridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, phenothiazine, phenoxazine, pyrazole, indazole, imidazole, benzimidazole, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, oxazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, benzothiazole, pyridazine, benzopyridazine, pyrimidine, benzopyrimidine, quinoxaline, 1,5-diazaanthracene, 2,7-diazapyrene, 2,3-diazapyrene, 1,6-diazapyrene, 1,8-diazapyrene, 4,5-diazapyrene, 4,5,9,10-tetraazaperylene, pyrazine, phenazine, phenoxazine, phenothiazine, fluorubine, naphthyridine, azacarbazole, benzocarboline, phenanthroline, 1,2,3-triazole, 1,2,4-triazole, benzotriazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, tetrazole, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, purine, pteridine, indolizine and benzothiadiazole.

For further illustration of the compound, one simple structure of formula (1) is shown in full and elucidated hereinafter

In this structure, the sub-ligand that coordinates to both metals M is a 2-phenylpyrimidine group. To the coordinating phenyl group is bonded a phenyl group to which one group of the formula (2) is bonded in each of the two ortho positions, i.e. V in this structure is a group of the formula (2) in each case. The central cycle therein is a phenyl group and the two A groups are each —HC═CH—, i.e. cis-alkenyl groups. To this group of the formula (2) are also bonded two sub-ligands L in each case, which, in the structure depicted above, are each phenylpyridine. Each of the two metals M, which are iridium here, is thus coordinated in the structure depicted above to two phenylpyridine ligands in each case and one phenylpyrimidine ligand, where the phenyl group and the pyrimidine group of the phenylpyrimidine each coordinate to both iridium atoms. The sub-ligands here are each joined by the group of the formula (2) to form a polypodal system.

The expression “bidentate sub-ligand” for L in the context of this application means that this unit would be a bidentate ligand if the group of the formula (2) or (3) were not present. However, as a result of the formal abstraction of a hydrogen atom in this bidentate ligand and the linkage within the bridge of the formula (2) or (3), it is not a separate ligand but a portion of the dodecadentate ligand which thus arises, i.e. a ligand having a total of 12 coordination sites, and so the term “sub-ligand” is used therefor.

The bond of the ligand to the metal M may either be a coordinate bond or a covalent bond, or the covalent fraction of the bond may vary according to the ligand. When it is said in the present application that the ligand or sub-ligand coordinates or binds to M, this refers in the context of the present application to any kind of bond of the ligand or sub-ligand to M, irrespective of the covalent fraction of the bond.

The compounds of the invention are preferably uncharged, meaning that they are electrically neutral. This is achieved in that Rh or Ir is in each case in the +III oxidation state. Each of the metals in that case is coordinated by two monoanionic bidentate sub-ligands and one dianionic tetradentate sub-ligand that binds to both metals, and so the sub-ligands compensate for the charge of the complexed metal atom.

As described above, the two metals M in the compound of the invention may be the same or different and are preferably in the +III oxidation state. Possible combinations are therefore Ir/Ir, Ir/Rh and Rh/Rh. In a preferred embodiment of the invention, both metals M are Ir(III).

In a preferred embodiment of the invention, the compounds of the formula (1) are selected from the compounds of the following formulae (1′), (1″) or (1′″):

where the R radicals in the ortho position to D and in the ortho position to the coordinating nitrogen atom shown explicitly in formula (1″) are each the same or different at each instance and are selected from the group consisting of H, D, F, CH₃ and CD₃ and are preferably H, and the other symbols used have the definitions detailed above.

In a preferred embodiment of the formula (1), in structures that coordinate to M via two six-membered (hetero)aryl groups of the central sub-ligand, each of the metals M is coordinated by one carbon atom and one nitrogen atom of the central sub-ligand and is also coordinated by two sub-ligands L in each case. In a further preferred embodiment of the formula (1), in structures that coordinate to M via a six-membered heteroaryl group and a five-membered heteroaryl group, in which E is C, of the central sub-ligand, one of the two metals M is coordinated by one carbon atom and one nitrogen atom and the other of the two metals M by two nitrogen atoms of the central sub-ligand. In addition, each metal is coordinated by two sub-ligands L. In a further preferred embodiment of the formula (1), in structures that coordinate to M via a six-membered (hetero)aryl group and a five-membered heteroaryl group, in which E is N, of the central sub-ligand, each of the metals M is coordinated by one carbon atom and one nitrogen atom of the central sub-ligand and is further coordinated by two sub-ligands L in each case.

The compound of the formula (1) thus preferably has a structure of one of the following formulae (1a) to (1h):

where the symbols used have the definitions given above and X in the five-membered ring of the formula (1d) to (1h) is the same or different at each instance and is CR or N.

In a preferred embodiment of the invention, X in the formulae (1a) to (1h) is CR.

In a further preferred embodiment of the invention, the explicitly detailed X² in formula (1), (1′), (1″), (1′″) and (1a) to (1h) are the same or different at each instance and are CR and more preferably CH, and X³ is C.

Preference is thus given to the compounds of the following formulae (1a′) to (1h′):

where the R radicals shown explicitly in ortho position to the coordinating carbon or nitrogen atoms are each the same or different at each instance and are selected from the group consisting of H, D, F, CH₃ and CD₃, and the other symbols used have the definitions given above. More preferably, the R radicals in ortho position to the coordinating carbon or nitrogen atoms in formulae (1a′) to (1h′) are H.

Particular preference is given to the structures of the formulae (1a) to (1c) or (1a′) and (1c′).

Recited hereinafter are preferred embodiments for V, i.e. the group of the formula (2) or (3).

When A² in formula (3) is CR, especially when all A² are CR, very particularly when, in addition, 0, 1, 2 or 3, especially 3, of the A¹ are CR₂, the R radicals on A² may assume different positions depending on the configuration. Preference is given here to small R radicals such as H or D. It is preferable that they are either all directed away from the metal (apical) or all directed inward toward the metal (endohedral). This is illustrated hereinafter by an example in which the A groups are each an ortho-phenylene group.

The third sub-ligand that coordinates to both metals M is not shown for the sake of clarity, but is merely indicated by the dotted bond. Preference is therefore given to complexes that can assume at least one of the two configurations. These are complexes in which all three sub-ligands are arranged equatorially on the central ring.

Suitable embodiments of the group of the formula (2) are the structures of the following formulae (5) to (8), and suitable embodiments of the group of the formula (3) are the structures of the following formulae (9) to (13):

where the symbols have the definitions given above.

Preferred R radicals in formulae (2), (3) and (5) to (13) are as follows:

-   R is the same or different at each instance and is H, D, F, CN, OR¹,     a straight-chain alkyl group having 1 to 10 carbon atoms or an     alkenyl group having 2 to 10 carbon atoms or a branched or cyclic     alkyl group having 3 to 10 carbon atoms, each of which may be     substituted by one or more R¹ radicals, or an aromatic or     heteroaromatic ring system which has 5 to 24 aromatic ring atoms and     may be substituted in each case by one or more R¹ radicals; -   R¹ is the same or different at each instance and is H, D, F, CN,     OR², a straight-chain alkyl group having 1 to 10 carbon atoms or an     alkenyl group having 2 to 10 carbon atoms or a branched or cyclic     alkyl group having 3 to 10 carbon atoms, each of which may be     substituted by one or more R² radicals, or an aromatic or     heteroaromatic ring system which has 5 to 24 aromatic ring atoms and     may be substituted in each case by one or more R² radicals; at the     same time, two or more adjacent R¹ radicals together may form a ring     system; -   R² is the same or different at each instance and is H, D, F or an     aliphatic, aromatic or heteroaromatic organic radical having 1 to 20     carbon atoms, in which one or more hydrogen atoms may also be     replaced by F.

Particularly preferred R radicals in formulae (2), (3) and (5) to (13) are as follows:

-   R is the same or different at each instance and is H, D, F, CN, a     straight-chain alkyl group having 1 to 4 carbon atoms or a branched     or cyclic alkyl group having 3 to 6 carbon atoms, each of which may     be substituted by one or more R¹ radicals, or an aromatic or     heteroaromatic ring system which has 6 to 12 aromatic ring atoms and     may be substituted in each case by one or more R¹ radicals; -   R¹ is the same or different at each instance and is H, D, F, CN, a     straight-chain alkyl group having 1 to 4 carbon atoms or a branched     or cyclic alkyl group having 3 to 6 carbon atoms, each of which may     be substituted by one or more R² radicals, or an aromatic or     heteroaromatic ring system which has 6 to 12 aromatic ring atoms and     may be substituted in each case by one or more R² radicals; at the     same time, two or more adjacent R¹ radicals together may form a ring     system; -   R² is the same or different at each instance and is H, D, F or an     aliphatic or aromatic hydrocarbyl radical having 1 to 12 carbon     atoms.

In a preferred embodiment of the invention, all X¹ groups in the group of the formula (2) are CR, and so the central trivalent cycle of the formula (2) is a benzene. More preferably, all X¹ groups are CH or CD, especially CH. In a further preferred embodiment of the invention, all X¹ groups are a nitrogen atom, and so the central trivalent cycle of the formula (2) is a triazine. Preferred embodiments of the formula (2) are thus the structures of the formulae (5) and (6) depicted above. More preferably, the structure of the formula (5) is a structure of the following formula (5′): Formula (5′)

where the symbols have the definitions given above.

In a further preferred embodiment of the invention, all A² groups in the group of the formula (3) are CR. More preferably, all A² groups are CH. Preferred embodiments of the formula (3) are thus the structures of the formula (9) depicted above. More preferably, the structure of the formula (9) is a structure of the following formula (9′) or (9″):

where the symbols have the definitions given above and R is preferably H.

There follows a description of preferred A groups as occur in the structures of the formulae (2) and (3) and (5) to (13). The A group may be the same or different at each instance and may be an alkenyl group, an amide group, an ester group, an alkylene group, a methylene ether group or an ortho-bonded arylene or heteroarylene group of the formula (4). When A is an alkenyl group, it is a cis-bonded alkenyl group. In the case of unsymmetric A groups, any orientation of the groups is possible. This is shown schematically hereinafter by the example of A=—C(═O)—O—. This gives rise to the following possible orientations of A, all of which are encompassed by the present invention:

In a preferred embodiment of the invention, A is the same or different, preferably the same, at each instance and is selected from the group consisting of —C(═O)—O—, —C(═O)—NR′— and a group of the formula (4). Further preferably, the two A groups are the same and also have the same substitution. Preferred combinations for the A groups within a formula (2) or (3) and the preferred embodiments are:

A A Formula (4) Formula (4) —C(═O)—O— —C(═O)—O— —C(═O)—NR′— —C(═O)—NR′— —C(═O)—O— Formula (4) —C(═O)—NR′— Formula (4) —C(═O)—O— —C(═O)—NR′—

When A is —C(═O)—NR′—, R′ is preferably the same or different at each instance and is a straight-chain alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms or an aromatic or heteroaromatic ring system which has 6 to 24 aromatic ring atoms, and may be substituted in each case by one or more R¹ radicals. More preferably, R′ is the same or different at each instance and is a straight-chain alkyl group having 1 to 5 carbon atoms or a branched or cyclic alkyl group having 3 to 6 carbon atoms or an aromatic or heteroaromatic ring system which has 6 to 12 aromatic ring atoms and may be substituted in each case by one or more R¹ radicals, but is preferably unsubstituted.

Preferred embodiments of the group of the formula (4) are described hereinafter. The group of the formula (4) may represent a heteroaromatic five-membered ring or an aromatic or heteroaromatic six-membered ring.

In a preferred embodiment of the invention, the group of the formula (4) contains not more than two heteroatoms in the aromatic or heteroaromatic unit, more preferably not more than one heteroatom. This does not mean that any substituents bonded to this group cannot also contain heteroatoms. In addition, this definition does not mean that formation of rings by substituents does not give rise to fused aromatic or heteroaromatic structures, for example naphthalene, benzimidazole, etc.

When both X³ groups in formula (4) are carbon atoms, preferred embodiments of the group of the formula (4) are the structures of the following formulae (14) to (30), and, when one X³ group is a carbon atom and the other X³ group in the same cycle is a nitrogen atom, preferred embodiments of the group of the formula (4) are the structures of the following formulae (31) to (38):

where the symbols have the definitions given above.

Particular preference is given to the six-membered aromatic rings and heteroaromatic rings of the formulae (14) to (18) depicted above. Very particular preference is given to ortho-phenylene, i.e. a group of the abovementioned formula (14).

At the same time, it is also possible for adjacent R substituents together to form a ring system, such that it is possible to form fused structures, including fused aryl and heteroaryl groups, for example naphthalene, quinoline, benzimidazole, carbazole, dibenzofuran or dibenzothiophene. Such ring formation is shown schematically below in groups of the abovementioned formula (14), which can lead, for example, to groups of the following formulae (14a) to (14j):

where the symbols have the definitions given above.

In general, the groups fused on may be fused onto any position in the unit of formula (4), as shown by the fused-on benzo group in the formulae (14a) to (14c). The groups as fused onto the unit of the formula (4) in the formulae (14d) to (14j) may therefore also be fused onto other positions in the unit of the formula (4).

The group of the formula (2) can more preferably be represented by the following formulae (2a) to (2i), and the group of the formula (3) can more preferably be represented by the following formulae (3a) to (3i):

where the symbols have the definitions given above. Preferably, X² is the same or different at each instance and is CR.

In a preferred embodiment of the invention, the group of the formulae (2a) to (2i) is selected from the groups of the formulae (5a′) to (5m′), and the group of the formulae (3a) to (3i) from the groups of the formulae (9a′) to (9i′):

where the symbols have the definitions given above. Preferably, X² is the same or different at each instance and is CR.

A particularly preferred embodiment of the group of the formula (2) is the group of the following formula (5a″):

where the symbols have the definitions given above.

More preferably, the R groups in the abovementioned formulae are the same or different and are H, D or an alkyl group having 1 to 4 carbon atoms. Most preferably, R═H. Very particular preference is thus given to the structure of the following formula (5a′″):

where the symbols have the definitions given above.

There follows a description of the bidentate monoanionic sub-ligands L. The sub-ligands L may be the same or different. It is preferable here when the two sub-ligands L that coordinate to the same metal M are each the same and also have the same substitution. The reason for this preference is the simpler synthesis of the corresponding ligands. In a particularly preferred embodiment, all four bidentate sub-ligands L are for the same and also have the same substitution.

In a further preferred embodiment of the invention, the coordinating atoms of the bidentate sub-ligands L are the same or different at each instance and are selected from C, N, P, O, S and/or B, more preferably C, N and/or O and most preferably C and/or N. These bidentate sub-ligands L preferably have one carbon atom and one nitrogen atom or two carbon atoms or two nitrogen atoms or two oxygen atoms or one oxygen atom and one nitrogen atom as coordinating atoms. In this case, the coordinating atoms of each of the sub-ligands L may be the same, or they may be different. Preferably, at least one of the two bidentate sub-ligands L that coordinate to the same metal M has one carbon atom and one nitrogen atom or two carbon atoms as coordinating atoms, especially one carbon atom and one nitrogen atom. More preferably, all bidentate sub-ligands have one carbon atom and one nitrogen atom or two carbon atoms as coordinating atoms, especially one carbon atom and one nitrogen atom. Particular preference is thus given to a metal complex in which all sub-ligands are ortho-metalated, i.e. form a metallacycle with the metal M in which at least one metal-carbon bond is present.

It is further preferable when the metallacycle which is formed from the metal M and the bidentate sub-ligand L is a five-membered ring, which is preferable particularly when the coordinating atoms are C and N, N and N, or N and O. When the coordinating atoms are O, a six-membered metallacyclic ring may also be preferred. This is shown schematically hereinafter:

where N is a coordinating nitrogen atom, C is a coordinating carbon atom and O represents coordinating oxygen atoms, and the carbon atoms shown are atoms of the bidentate sub-ligand L.

In a preferred embodiment of the invention, at least one of the bidentate sub-ligands L per metal M and more preferably all bidentate sub-ligands are the same or different at each instance and are selected from the structures of the following formulae (L-1), (L-2) and (L-3):

where the dotted bond represents the bond of the sub-ligand L to the group of the formula (2) or (3) or the preferred embodiments and the other symbols used are as follows:

-   CyC is the same or different at each instance and is a substituted     or unsubstituted aryl or heteroaryl group which has 5 to 14 aromatic     ring atoms and coordinates to M via a carbon atom and is bonded to     CyD via a covalent bond; -   CyD is the same or different at each instance and is a substituted     or unsubstituted heteroaryl group which has 5 to 14 aromatic ring     atoms and coordinates to M via a nitrogen atom or via a carbene     carbon atom and is bonded to CyC via a covalent bond;     at the same time, two or more of the optional substituents together     may form a ring system; in addition, the optional radicals are     preferably selected from the abovementioned R radicals.

At the same time, CyD in the sub-ligands of the formulae (L-1) and (L-2) preferably coordinates via an uncharged nitrogen atom or via a carbene carbon atom, especially via an uncharged nitrogen atom. Further preferably, one of the two CyD groups in the ligand of the formula (L-3) coordinates via an uncharged nitrogen atom and the other of the two CyD groups via an anionic nitrogen atom. Further preferably, CyC in the sub-ligands of the formulae (L-1) and (L-2) coordinates via anionic carbon atoms.

When two or more of the substituents, especially two or more R radicals, together form a ring system, it is possible for a ring system to be formed from substituents bonded to directly adjacent carbon atoms. In addition, it is also possible that the substituents on CyC and CyD in the formulae (L-1) and (L-2) or the substituents on the two CyD groups in formula (L-3) together form a ring, as a result of which CyC and CyD or the two CyD groups may also together form a single fused aryl or heteroaryl group as bidentate ligand.

In a preferred embodiment of the present invention, CyC is an aryl or heteroaryl group having 6 to 13 aromatic ring atoms, more preferably having 6 to 10 aromatic ring atoms, most preferably having 6 aromatic ring atoms, especially a phenyl group, which coordinates to the metal via a carbon atom, which may be substituted by one or more R radicals and which is bonded to CyD via a covalent bond.

Preferred embodiments of the CyC group are the structures of the following formulae (CyC-1) to (CyC-20):

where CyC binds in each case to the position in CyD indicated by # and coordinates to the metal at the position indicated by *, R has the definitions given above and the further symbols used are as follows:

-   X is the same or different at each instance and is CR or N, with the     proviso that not more than two symbols X per cycle are N; -   W is NR, O or S;     with the proviso that, when the sub-ligand L is bonded via CyC     within the group of the formula (2) or (3), one symbol X is C and     the bridge of the formula (2) or (3) or the preferred embodiments is     bonded to this carbon atom. When the sub-ligand L is bonded via the     CyC group to the group of the formula (2) or (3), the bond is     preferably via the position marked by “o” in the formulae depicted     above, and so the symbol X marked by “o” in that case is     preferably C. The above-depicted structures which do not contain any     symbol X marked by “o” are preferably not bonded to the group of the     formula (2) or (3), since such a bond to the bridge is not     advantageous for steric reasons.

Preferably, a total of not more than two symbols X in CyC are N, more preferably not more than one symbol X in CyC is N, and most preferably all symbols X are CR, with the proviso that, when CyC is bonded directly within the group of the formula (2) or (3), one symbol X is C and the bridge of the formula (2) or (3) or the preferred embodiments is bonded to this carbon atom.

Particularly preferred CyC groups are the groups of the following formulae (CyC-1a) to (CyC-20a):

where the symbols have the definitions given above and, when CyC is bonded directly within the group of the formula (2) or (3), one R radical is not present and the group of the formula (2) or (3) or the preferred embodiments is bonded to the corresponding carbon atom. When the CyC group is bonded directly to the group of the formula (2) or (3), the bond is preferably via the position marked by “o” in the formulae depicted above, and so the R radical in this position in that case is preferably absent. The above-depicted structures which do not contain any carbon atom marked by “o” are preferably not bonded directly to the group of the formula (2) or (3).

Preferred groups among the (CyC-1) to (CyC-20) groups are the (CyC-1), (CyC-3), (CyC-8), (CyC-10), (CyC-12), (CyC-13) and (CyC-16) groups, and particular preference is given to the (CyC-1a), (CyC-3a), (CyC-8a), (CyC-10a), (CyC-12a), (CyC-13a) and (CyC-16a) groups.

In a further preferred embodiment of the invention, CyD is a heteroaryl group having 5 to 13 aromatic ring atoms, more preferably having 6 to 10 aromatic ring atoms, which coordinates to the metal via an uncharged nitrogen atom or via a carbene carbon atom and which may be substituted by one or more R radicals and which is bonded via a covalent bond to CyC.

Preferred embodiments of the CyD group are the structures of the following formulae (CyD-1) to (CyD-14):

where the CyD group binds to CyC in each case at the position indicated by # and coordinates to the metal at the position indicated by *, and where X, W and R have the definitions given above, with the proviso that, when CyD is bonded directly within the group of the formula (2) or (3), one symbol X is C and the bridge of the formula (2) or (3) or the preferred embodiments is bonded to this carbon atom. When the CyD group is bonded directly to the group of the formula (2) or (3), the bond is preferably via the position marked by “o” in the formulae depicted above, and so the symbol X marked by “o” in that case is preferably C. The above-depicted structures which do not contain any symbol X marked by “o” are preferably not bonded directly to the group of the formula (2) or (3), since such a bond to the bridge is not advantageous for steric reasons.

In this case, the (CyD-1) to (CyD-4), (CyD-7) to (CyD-10), (CyD-13) and (CyD-14) groups coordinate to the metal via an uncharged nitrogen atom, the (CyD-5) and (CyD-6) groups via a carbene carbon atom and the (CyD-11) and (CyD-12) groups via an anionic nitrogen atom.

Preferably, a total of not more than two symbols X in CyD are N, more preferably not more than one symbol X in CyD is N, and especially preferably all symbols X are CR, with the proviso that, when CyD is bonded directly within the group of the formula (2) or (3), one symbol X is C and the bridge of the formula (2) or (3) or the preferred embodiments is bonded to this carbon atom.

Particularly preferred CyD groups are the groups of the following formulae (CyD-1a) to (CyD-14b):

where the symbols used have the definitions given above and, when CyD is bonded directly within the group of the formula (2) or (3), one R radical is not present and the bridge of the formula (2) or (3) or the preferred embodiments is bonded to the corresponding carbon atom. When CyD is bonded directly to the group of the formula (2) or (3), the bond is preferably via the position marked by “o” in the formulae depicted above, and so the R radical in this position in that case is preferably absent. The above-depicted structures which do not contain any carbon atom marked by “o” are preferably not bonded directly to the group of the formula (2) or (3).

Preferred groups among the (CyD-1) to (CyD-14) groups are the (CyD-1), (CyD-2), (CyD-3), (CyD-4), (CyD-5) and (CyD-6) groups, especially (CyD-1), (CyD-2) and (CyD-3), and particular preference is given to the (CyD-1a), (CyD-2a), (CyD-3a), (CyD-4a), (CyD-5a) and (CyD-6a) groups, especially (CyD-1a), (CyD-2a) and (CyD-3a).

In a preferred embodiment of the present invention, CyC is an aryl or heteroaryl group having 6 to 13 aromatic ring atoms, and at the same time CyD is a heteroaryl group having 5 to 13 aromatic ring atoms. More preferably, CyC is an aryl or heteroaryl group having 6 to 10 aromatic ring atoms, and at the same time CyD is a heteroaryl group having 5 to 10 aromatic ring atoms. Most preferably, CyC is an aryl or heteroaryl group having 6 aromatic ring atoms, especially phenyl, and CyD is a heteroaryl group having 6 to 10 aromatic ring atoms. At the same time, CyC and CyD may be substituted by one or more R radicals.

The abovementioned preferred (CyC-1) to (CyC-20) and (CyD-1) to (CyD-14) groups may be combined with one another as desired in the sub-ligands of the formulae (L-1) and (L-2), provided that at least one of the CyC or CyD groups has a suitable attachment site to the group of the formula (2) or (3), suitable attachment sites being signified by “o” in the formulae given above. It is especially preferable when the CyC and CyD groups specified above as particularly preferred, i.e. the groups of the formulae (CyC-1a) to (CyC-20a) and the groups of the formulae (CyD1-a) to (CyD-14b), are combined with one another, provided that at least one of the preferred CyC or CyD groups has a suitable attachment site to the group of the formula (2) or (3), suitable attachment sites being signified by “o” in the formulae given above. Combinations in which neither CyC nor CyD has such a suitable attachment site to the bridge of the formula (2) or (3) are therefore not preferred.

It is very particularly preferable when one of the (CyC-1), (CyC-3), (CyC-8), (CyC-10), (CyC-12), (CyC-13) and (CyC-16) groups and especially the (CyC-1a), (CyC-3a), (CyC-8a), (CyC-10a), (CyC-12a), (CyC-13a) and (CyC-16a) groups is combined with one of the (CyD-1), (CyD-2) and (CyD-3) groups and especially with one of the (CyD-1a), (CyD-2a) and (CyD-3a) groups.

Preferred sub-ligands (L-1) are the structures of the following formulae (L-1-1) and (L-1-2), and preferred sub-ligands (L-2) are the structures of the following formulae (L-2-1) to (L-2-3):

where the symbols used have the definitions given above, * indicates the position of the coordination to the iridium and “o” represents the position of the bond to the group of the formula (2) or (3).

Particularly preferred sub-ligands (L-1) are the structures of the following formulae (L-1-1a) and (L-1-2b), and particularly preferred sub-ligands (L-2) are the structures of the following formulae (L-2-1a) to (L-2-3a):

where the symbols used have the definitions given above and “o” represents the position of the bond to the group of the formula (2) or (3).

It is likewise possible for the abovementioned preferred CyD groups in the sub-ligands of the formula (L-3) to be combined with one another as desired, by combining and uncharged CyD group, i.e. a (CyD-1) to (CyD-10), (CyD-13) or (CyD-14) group, with an anionic CyD group, i.e. a (CyD-11) or (CyD-12) group, provided that at least one of the preferred CyD groups has a suitable attachment site to the group of the formula (2) or (3), suitable attachment sites being signified by “o” in the formulae given above.

When two R radicals, one of them bonded to CyC and the other to CyD in the formulae (L-1) and (L-2) or one of them bonded to one CyD group and the other to the other CyD group in formula (L-3), form an aromatic ring system with one another, this may result in bridged sub-ligands and also in sub-ligands which represent a single larger heteroaryl group overall, for example benzo[h]quinoline, etc. The ring formation between the substituents on CyC and CyD in the formulae (L-1) and (L-2) or between the substituents on the two CyD groups in formula (L-3) is preferably via a group according to one of the following formulae (39) to (48):

where R¹ has the definitions given above and the dotted bonds signify the bonds to CyC or CyD. At the same time, the unsymmetric groups among those mentioned above may be incorporated in each of the two possible orientations; for example, in the group of the formula (48), the oxygen atom may bind to the CyC group and the carbonyl group to the CyD group, or the oxygen atom may bind to the CyD group and the carbonyl group to the CyC group.

At the same time, the group of the formula (45) is preferred particularly when this results in ring formation to give a six-membered ring, as shown below, for example, by the formulae (L-22) and (L-23).

Preferred ligands which arise through ring formation between two R radicals in the different cycles are the structures of the formulae (L-4) to (L-31) shown below:

where the symbols used have the definitions given above and “o” indicates the position at which this sub-ligand is joined to the group of the formula (2) or (3).

In a preferred embodiment of the sub-ligands of the formulae (L-4) to (L-31), a total of one symbol X is N and the other symbols X are CR, or all symbols X are CR.

In a further embodiment of the invention, it is preferable if, in the groups (CyC-1) to (CyC-20) or (CyD-1) to (CyD-14) or in the sub-ligands (L-1-1) to (L-2-3), (L-4) to (L-31), one of the atoms X is N when an R group bonded as a substituent adjacent to this nitrogen atom is not hydrogen or deuterium. This applies analogously to the preferred structures (CyC-1a) to (CyC-20a) or (CyD-1a) to (CyD-14b) in which a substituent bonded adjacent to a non-coordinating nitrogen atom is preferably an R group which is not hydrogen or deuterium. In this case, this substituent R is preferably a group selected from CF₃, OR¹ where R¹ is an alkyl group having 1 to 10 carbon atoms, alkyl groups having 1 to 10 carbon atoms, especially branched or cyclic alkyl groups having 3 to 10 carbon atoms, a dialkylamino group having 2 to 10 carbon atoms, aromatic or heteroaromatic ring systems or aralkyl or heteroaralkyl groups. These groups are sterically demanding groups. Further preferably, this R radical may also form a cycle with an adjacent R radical.

A further suitable bidentate sub-ligand is the sub-ligand of the following formula (L-32) or (L-33)

where R has the definitions given above, * represents the position of coordination to the metal, “o” represents the position of linkage of the sub-ligand to the group of the formula (2) or (3) and the other symbols used are as follows:

-   X is the same or different at each instance and is CR or N, with the     proviso that not more than one symbol X per cycle is N, and     additionally with the proviso that one symbol X is C and the     sub-ligand is bonded within the group of the formula (2) or (3) via     this carbon atom.

When two R radicals bonded to adjacent carbon atoms in the sub-ligands (L-32) and (L-33) form an aromatic cycle with one another, this cycle together with the two adjacent carbon atoms is preferably a structure of the following formula (49):

where the dotted bonds symbolize the linkage of this group within the sub-ligand and Y is the same or different at each instance and is CR¹ or N and preferably not more than one symbol Y is N. In a preferred embodiment of the sub-ligand (L-32) or (L-33), not more than one group of the formula (50) is present. In a preferred embodiment of the invention, in the sub-ligand of the formulae (L-32) and (L-33), a total of 0, 1 or 2 of the symbols X and, if present, Y are N. More preferably, a total of 0 or 1 of the symbols X and, if present, Y are N.

Further suitable bidentate sub-ligands are the structures of the following formulae (L-34) to (L-38), where preferably not more than one of the two bidentate sub-ligands L per metal is one of these structures,

where the sub-ligands (L-34) to (L-36) each coordinate to the metal via the nitrogen atom explicitly shown and the negatively charged oxygen atom, and the sub-ligands (L-37) and (L-38) coordinate to the metal via the two oxygen atoms, X has the definitions given above and “o” indicates the position via which the sub-ligand L is joined to the group of the formula (2) or (3).

The above-recited preferred embodiments of X are also preferred for the sub-ligands of the formulae (L-34) to (L-36).

Preferred sub-ligands of the formulae (L-34) to (L-36) are therefore the sub-ligands of the following formulae (L-34a) to (L-36a):

where the symbols used have the definitions given above and “o” indicates the position via which the sub-ligand L is joined to the group of the formula (2) or (3).

More preferably, in these formulae, R is hydrogen, where “o” indicates the position via which the sub-ligand L is joined within the group of the formula (2) or (3) or the preferred embodiments, and so the structures are those of the following formulae (L-34b) to (L-36b):

where the symbols used have the definitions given above.

There follows a description of preferred substituents as may be present on the above-described sub-ligands, but also on A when A is a group of the formula (4).

In a preferred embodiment of the invention, the compound of the invention contains two substituents R which are bonded to adjacent carbon atoms and together form an aliphatic ring according to one of the formulae described hereinafter. In this case, the two R substituents which form this aliphatic ring may be present on the bridge of the formulae (2) or (3) or the preferred embodiments and/or on one or more of the bidentate sub-ligands L. The aliphatic ring which is formed by the ring formation by two substituents R together is preferably described by one of the following formulae (50) to (56):

where R¹ and R² have the definitions given above, the dotted bonds signify the linkage of the two carbon atoms in the ligand and, in addition:

-   Z¹, Z³ is the same or different at each instance and is C(R³)₂, O,     S, NR³ or C(═O); -   Z² is C(R¹)₂, O, S, NR³ or C(═O); -   G is an alkylene group which has 1, 2 or 3 carbon atoms and may be     substituted by one or more R² radicals, —CR²═CR²— or an ortho-bonded     arylene or heteroarylene group which has 5 to 14 aromatic ring atoms     and may be substituted by one or more R² radicals; -   R³ is the same or different at each instance and is H, F, a     straight-chain alkyl or alkoxy group having 1 to 10 carbon atoms, a     branched or cyclic alkyl or alkoxy group having 3 to 10 carbon     atoms, where the alkyl or alkoxy group may be substituted in each     case by one or more R² radicals, where one or more nonadjacent CH₂     groups may be replaced by R²C═CR², C≡C, Si(R²)₂, C═O, NR², O, S or     CONR², or an aromatic or heteroaromatic ring system which has 5 to     24 aromatic ring atoms and may be substituted in each case by one or     more R² radicals, or an aryloxy or heteroaryloxy group which has 5     to 24 aromatic ring atoms and may be substituted by one or more R²     radicals; at the same time, two R³ radicals bonded to the same     carbon atom together may form an aliphatic or aromatic ring system     and thus form a spiro system; in addition, R³ with an adjacent R or     R¹ radical may form an aliphatic ring system;     with the proviso that no two heteroatoms in these groups are bonded     directly to one another and no two C═O groups are bonded directly to     one another.

In a preferred embodiment of the invention, R³ is not H.

In the above-depicted structures of the formulae (50) to (56) and the further embodiments of these structures specified as preferred, a double bond is depicted in a formal sense between the two carbon atoms. This is a simplification of the chemical structure when these two carbon atoms are incorporated into an aromatic or heteroaromatic system and hence the bond between these two carbon atoms is formally between the bonding level of a single bond and that of a double bond. The drawing of the formal double bond should thus not be interpreted so as to limit the structure; instead, it will be apparent to the person skilled in the art that this is an aromatic bond.

When adjacent radicals in the structures of the invention form an aliphatic ring system, it is preferable when the latter does not have any acidic benzylic protons. Benzylic protons are understood to mean protons which bind to a carbon atom bonded directly to the ligand. This can be achieved by virtue of the carbon atoms in the aliphatic ring system which bind directly to an aryl or heteroaryl group being fully substituted and not containing any bonded hydrogen atoms. Thus, the absence of acidic benzylic protons in the formulae (50) to (52) is achieved by virtue of Z¹ and Z³, when they are C(R³)₂, being defined such that R³ is not hydrogen. This can additionally also be achieved by virtue of the carbon atoms in the aliphatic ring system which bind directly to an aryl or heteroaryl group being the bridgeheads in a bi- or polycyclic structure. The protons bonded to bridgehead carbon atoms, because of the spatial structure of the bi- or polycycle, are significantly less acidic than benzylic protons on carbon atoms which are not bonded within a bi- or polycyclic structure, and are regarded as non-acidic protons in the context of the present invention. Thus, the absence of acidic benzylic protons in formulae (53) to (56) is achieved by virtue of this being a bicyclic structure, as a result of which R¹, when it is H, is much less acidic than benzylic protons since the corresponding anion of the bicyclic structure is not mesomerically stabilized. Even when R¹ in formulae (53) to (56) is H, this is therefore a non-acidic proton in the context of the present application.

In a preferred embodiment of the structure of the formulae (50) to (56), not more than one of the Z¹, Z² and Z³ groups is a heteroatom, especially O or NR³, and the other groups are C(R³)₂ or C(R¹)₂, or Z¹ and Z³ are the same or different at each instance and are O or NR³ and Z² is C(R¹)₂. In a particularly preferred embodiment of the invention, Z¹ and Z³ are the same or different at each instance and are C(R³)₂, and Z² is C(R¹)₂ and more preferably C(R³)₂ or CH₂.

Preferred embodiments of the formula (50) are thus the structures of the formulae (50-A), (50-B), (50-C) and (50-D), and a particularly preferred embodiment of the formula (50-A) is the structures of the formulae (50-E) and (50-F):

where R¹ and R³ have the definitions given above and Z¹, Z² and Z³ are the same or different at each instance and are O or NR³.

Preferred embodiments of the formula (51) are the structures of the following formulae (51-A) to (51-F):

where R¹ and R³ have the definitions given above and Z¹, Z² and Z³ are the same or different at each instance and are O or NR³.

Preferred embodiments of the formula (52) are the structures of the following formulae (52-A) to (52-E):

where R¹ and R³ have the definitions given above and Z¹, Z² and Z³ are the same or different at each instance and are 0 or NR³.

In a preferred embodiment of the structure of formula (53), the R¹ radicals bonded to the bridgehead are H, D, F or CH₃. Further preferably, Z² is C(R¹)₂ or O, and more preferably C(R³)₂. Preferred embodiments of the formula (53) are thus structures of the formulae (53-A) and (53-B), and a particularly preferred embodiment of the formula (53-A) is a structure of the formula (53-C):

where the symbols used have the definitions given above.

Further preferably, the G group in the formulae (53), (53-A), (53-B), (53-C), (54), (54-A), (55), (55-A), (56) and (56-A) is a 1,2-ethylene group which may be substituted by one or more R² radicals, where R² is preferably the same or different at each instance and is H or an alkyl group having 1 to 4 carbon atoms, or an ortho-arylene group which has 6 to 10 carbon atoms and may be substituted by one or more R² radicals, but is preferably unsubstituted, especially an ortho-phenylene group which may be substituted by one or more R² radicals, but is preferably unsubstituted.

In a further preferred embodiment of the invention, R³ in the groups of the formulae (50) to (56) and in the preferred embodiments is the same or different at each instance and is F, a straight-chain alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, where one or more nonadjacent CH₂ groups in each case may be replaced by R²C═CR² and one or more hydrogen atoms may be replaced by D or F, or an aromatic or heteroaromatic ring system which has 5 to 14 aromatic ring atoms and may be substituted in each case by one or more R² radicals; at the same time, two R³ radicals bonded to the same carbon atom may together form an aliphatic or aromatic ring system and thus form a spiro system; in addition, R³ may form an aliphatic ring system with an adjacent R or R¹ radical.

In a particularly preferred embodiment of the invention, R³ in the groups of the formulae (50) to (56) and in the preferred embodiments is the same or different at each instance and is F, a straight-chain alkyl group having 1 to 3 carbon atoms, especially methyl, or an aromatic or heteroaromatic ring system which has 5 to 12 aromatic ring atoms and may be substituted in each case by one or more R² radicals, but is preferably unsubstituted; at the same time, two R³ radicals bonded to the same carbon atom may together form an aliphatic or aromatic ring system and thus form a spiro system; in addition, R³ may form an aliphatic ring system with an adjacent R or R¹ radical.

Examples of particularly suitable groups of the formula (50) are the groups depicted below:

Examples of particularly suitable groups of the formula (51) are the groups depicted below:

Examples of particularly suitable groups of the formulae (52), (55) and (56) are the groups depicted below:

Examples of particularly suitable groups of the formula (53) are the groups depicted below:

Examples of particularly suitable groups of the formula (54) are the groups depicted below:

When R radicals are bonded within the bidentate sub-ligands or ligands or within the bivalent arylene or heteroarylene groups of the formula (4) bonded within the formulae (2) to (3) or the preferred embodiments, these R radicals are the same or different at each instance and are preferably selected from the group consisting of H, D, F, Br, I, N(R¹)₂, OR¹, CN, Si(R¹)₃, B(OR¹)₂, C(═O)R¹, a straight-chain alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, where the alkyl or alkenyl group may be substituted in each case by one or more R¹ radicals, or an aromatic or heteroaromatic ring system which has 5 to 30 aromatic ring atoms and may be substituted in each case by one or more R¹ radicals; at the same time, two adjacent R radicals together or R together with R¹ may also form a mono- or polycyclic, aliphatic or aromatic ring system. More preferably, these R radicals are the same or different at each instance and are selected from the group consisting of H, D, F, N(R¹)₂, a straight-chain alkyl group having 1 to 6 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, where one or more hydrogen atoms may be replaced by D or F, or an aromatic or heteroaromatic ring system which has 5 to 24 aromatic ring atoms, preferably 6 to 13 aromatic ring atoms, and may be substituted in each case by one or more R¹ radicals; at the same time, two adjacent R radicals together or R together with R¹ may also form a mono- or polycyclic, aliphatic or aromatic ring system.

Preferred R¹ radicals bonded to R are the same or different at each instance and are H, D, F, N(R²)₂, OR², CN, a straight-chain alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, where the alkyl group may be substituted in each case by one or more R² radicals, or an aromatic or heteroaromatic ring system which has 5 to 24 aromatic ring atoms and may be substituted in each case by one or more R² radicals; at the same time, two or more adjacent R¹ radicals together may form a mono- or polycyclic aliphatic ring system. Particularly preferred R¹ radicals bonded to R are the same or different at each instance and are H, F, CN, a straight-chain alkyl group having 1 to 5 carbon atoms or a branched or cyclic alkyl group having 3 to 5 carbon atoms, each of which may be substituted by one or more R² radicals, or an aromatic or heteroaromatic ring system which has 5 to 13 aromatic ring atoms, preferably 6 to 13 aromatic ring atoms, and may be substituted in each case by one or more R² radicals; at the same time, two or more adjacent R¹ radicals together may form a mono- or polycyclic aliphatic ring system.

Preferred R² radicals are the same or different at each instance and are H, F or an aliphatic hydrocarbyl radical having 1 to 5 carbon atoms or an aromatic hydrocarbyl radical having 6 to 12 carbon atoms; at the same time, two or more R² substituents together may also form a mono- or polycyclic aliphatic ring system.

The abovementioned preferred embodiments can be combined with one another as desired. In a particularly preferred embodiment of the invention, the abovementioned preferred embodiments apply simultaneously.

Examples of bimetallic complexes of the invention are the structures adduced below.

The compounds of the invention are chiral structures. According to the exact structure of the complexes and ligands, the formation of diastereomers and of several pairs of enantiomers is possible. In that case, the complexes of the invention include both the mixtures of the different diastereomers or the corresponding racemates and the individual isolated diastereomers or enantiomers.

In the ortho-metalation reaction of the ligands, the corresponding bimetallic complexes are typically obtained as a mixture of ΛΛ and ΔΔ isomers and ΔΛ and ΛΔ isomers. ΛΛ and ΔΔ isomers form one pair of enantiomers, as do the ΔΛ and ΛΔ isomers. The diastereomer pairs can be separated by conventional methods, e.g. by chromatography or by fractional crystallization. According to the symmetry of the ligands, stereocenters may coincide, and so meso forms are also possible. For example, the ortho-metalation of C_(2v)- or C_(s)-symmetric ligands typically affords ΛΛ and ΔΔ isomers (racemate, C₂-symmetric) and an ΛΔ isomer (meso compound, C_(s)-symmetric).

Typically, the complexes in the ortho-metalation are obtained as a mixture of diastereomer pairs. However, it is also possible to selectively synthesize just one of the pairs of diastereomers since the other, according to ligand structure, forms only in small amounts, if at all, for steric reasons. This is to be shown by the example which follows.

Owing to the unfavorable steric interaction of two phenylpyridine ligands in the case of the ΔΛ isomer (the two ligands butt against one another, out of the plane of the drawing), the ΔΛ isomer (meso form) does not form. The ortho-metalation of the ligand forms solely the racemate of ΔΔ and ΛΛ isomers.

The racemate separation of the ΔΔ and ΛΛ isomers can be effected via fractional crystallization of diastereomeric pairs of salts or on chiral columns by customary methods. One option for this purpose is to oxidize the uncharged Ir(III) complexes (for example with peroxides or H₂O₂ or by electrochemical means), add the salt of an enantiomerically pure monoanionic base (chiral base) to the cationic Ir(III)/Ir(IV) complexes thus produced or the dicationic Ir(IV)/Ir(IV) complexes, separate the diastereomeric salts thus produced by fractional crystallization, and then reduce them with the aid of a reducing agent (e.g. zinc, hydrazine hydrate, ascorbic acid, etc.) to give the enantiomerically pure uncharged complex, as shown schematically below:

Enantiomerically pure complexes can also be synthesized selectively, as shown in the scheme which follows. For this purpose, as described above, the isomer pair formed in the ortho-metalation is brominated and then reacted with a boronic acid R*A-B(OH)₂ containing a chiral R* radical (enantiomeric excess preferably >99%) via cross-coupling reaction, as described in general terms in the as yet unpublished application EP 16177095.3. The diastereomer pairs formed can be separated by chromatography on silica gel or by fractional crystallization by customary methods. In this way, enantiomerically enriched or enantiomerically pure complexes are obtained. Subsequently, the chiral group can optionally be eliminated or else can remain in the molecule.

The complexes of the invention can especially be prepared by the route described hereinafter. For this purpose, the 12-dentate ligand is prepared and then coordinated to the metals M by an ortho-metalation reaction. In general, for this purpose, an iridium salt or rhodium salt is reacted with the corresponding free ligand.

Therefore, the present invention further provides a process for preparing the compound of the invention by reacting the corresponding free ligands with metal alkoxides of the formula (57), with metal ketoketonates of the formula (58), with metal halides of the formula (59) or with metal carboxylates of the formula (60)

where M and R have the definitions given above, Hal=F, Cl, Br or I and the iridium reactants or rhodium reactants may also take the form of the corresponding hydrates. R here is preferably an alkyl group having 1 to 4 carbon atoms.

It is likewise possible to use iridium compounds or rhodium compounds bearing both alkoxide and/or halide and/or hydroxyl radicals and ketoketonate radicals. These compounds may also be charged. Corresponding iridium compounds of particular suitability as reactants are disclosed in WO 2004/085449. Particularly suitable are [IrCl₂(acac)₂]-, for example Na[IrCl₂(acac)₂], metal complexes with acetylacetonate derivatives as ligand, for example Ir(acac)₃ or tris(2,2,6,6-tetramethylheptane-3,5-dionato)iridium, and IrCl₃.xH₂O where x is typically a number from 2 to 4.

The synthesis of the complexes is preferably conducted as described in WO 2002/060910 and in WO 2004/085449. In this case, the synthesis can, for example, also be activated by thermal or photochemical means and/or by microwave radiation. In addition, the synthesis can also be conducted in an autoclave at elevated pressure and/or elevated temperature.

The reactions can be conducted without addition of solvents or melting aids in a melt of the corresponding ligands to be o-metalated. It is optionally possible to add solvents or melting aids. Suitable solvents are protic or aprotic solvents such as aliphatic and/or aromatic alcohols (methanol, ethanol, isopropanol, t-butanol, etc.), oligo- and polyalcohols (ethylene glycol, propane-1,2-diol, glycerol, etc.), alcohol ethers (ethoxyethanol, diethylene glycol, triethylene glycol, polyethylene glycol, etc.), ethers (di- and triethylene glycol dimethyl ether, diphenyl ether, etc.), aromatic, heteroaromatic and/or aliphatic hydrocarbons (toluene, xylene, mesitylene, chlorobenzene, pyridine, lutidine, quinoline, isoquinoline, tridecane, hexadecane, etc.), amides (DMF, DMAC, etc.), lactams (NMP), sulfoxides (DMSO) or sulfones (dimethyl sulfone, sulfolane, etc.). Suitable melting aids are compounds that are in solid form at room temperature but melt when the reaction mixture is heated and dissolve the reactants, so as to form a homogeneous melt. Particularly suitable are biphenyl, m-terphenyl, triphenyls, R- or S-binaphthol or else the corresponding racemate, 1,2-, 1,3- or 1,4-bisphenoxybenzene, triphenylphosphine oxide, 18-crown-6, phenol, 1-naphthol, hydroquinone, etc. Particular preference is given here to the use of hydroquinone.

It is possible by these processes, if necessary followed by purification, for example recrystallization or sublimation, to obtain the inventive compounds of formula (1) in high purity, preferably more than 99% (determined by means of ¹H NMR and/or HPLC).

The compounds of the invention may also be rendered soluble by suitable substitution, for example by comparatively long alkyl groups (about 4 to 20 carbon atoms), especially branched alkyl groups, or optionally substituted aryl groups, for example xylyl, mesityl or branched terphenyl or quaterphenyl groups. Another particular method that leads to a distinct improvement in the solubility of the metal complexes is the use of fused-on aliphatic groups, as shown, for example, by the formulae (50) to (56) disclosed above. Such compounds are then soluble in sufficient concentration at room temperature in standard organic solvents, for example toluene or xylene, to be able to process the complexes from solution. These soluble compounds are of particularly good suitability for processing from solution, for example by printing methods.

For the processing of the metal complexes of the invention from the liquid phase, for example by spin-coating or by printing methods, formulations of the metal complexes of the invention are required. These formulations may, for example, be solutions, dispersions or emulsions. For this purpose, it may be preferable to use mixtures of two or more solvents. Suitable and preferred solvents are, for example, toluene, anisole, o-, m- or p-xylene, methyl benzoate, mesitylene, tetralin, veratrole, THF, methyl-THF, THP, chlorobenzene, dioxane, phenoxytoluene, especially 3-phenoxytoluene, (−)-fenchone, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, 1-methylnaphthalene, 2-methylbenzothiazole, 2-phenoxyethanol, 2-pyrrolidinone, 3-methylanisole, 4-methylanisole, 3,4-dimethylanisole, 3,5-dimethylanisole, acetophenone, α-terpineol, benzothiazole, butyl benzoate, cumene, cyclohexanol, cyclohexanone, cyclohexylbenzene, decalin, dodecylbenzene, ethyl benzoate, indane, NMP, p-cymene, phenetole, 1,4-diisopropylbenzene, dibenzyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, diethylene glycol monobutyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 2-isopropylnaphthalene, pentylbenzene, hexylbenzene, heptylbenzene, octylbenzene, 1,1-bis(3,4-dimethylphenyl)ethane, hexamethylindane, 2-methylbiphenyl, 3-methylbiphenyl, 1-methylnaphthalene, 1-ethylnaphthalene, ethyl octanoate, diethyl sebacate, octyl octanoate, heptylbenzene, menthyl isovalerate, cyclohexyl hexanoate or mixtures of these solvents.

The present invention therefore further provides a formulation comprising at least one compound of the invention and at least one further compound.

The further compound may, for example, be a solvent, especially one of the abovementioned solvents or a mixture of these solvents. The further compound may alternatively be a further organic or inorganic compound which is likewise used in the electronic device, for example a matrix material. This further compound may also be polymeric.

The compound of the invention can be used in the electronic device as active component or as oxygen sensitizers. The present invention thus further provides for the use of a compound of the invention in an electronic device or as oxygen sensitizer. The present invention still further provides an electronic device comprising at least one compound of the invention.

An electronic device is understood to mean any device comprising anode, cathode and at least one layer, said layer comprising at least one organic or organometallic compound. The electronic device of the invention thus comprises anode, cathode and at least one layer containing at least one metal complex of the invention. Preferred electronic devices are selected from the group consisting of organic electroluminescent devices (OLEDs, PLEDs), organic infrared electroluminescence sensors, organic integrated circuits (O-ICs), organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic light-emitting transistors (O-LETs), organic solar cells (O-SCs), the latter being understood to mean both purely organic solar cells and dye-sensitized solar cells (Grätzel cells), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQDs), light-emitting electrochemical cells (LECs), oxygen sensors and organic laser diodes (O-lasers), comprising at least one metal complex of the invention in at least one layer. Particular preference is given to organic electroluminescent devices. Active components are generally the organic or inorganic materials introduced between the anode and cathode, for example charge injection, charge transport or charge blocker materials, but especially emission materials and matrix materials. The compounds of the invention exhibit particularly good properties as emission material in organic electroluminescent devices. A preferred embodiment of the invention is therefore organic electroluminescent devices. In addition, the compounds of the invention can be used for production of singlet oxygen or in photocatalysis.

The organic electroluminescent device comprises cathode, anode and at least one emitting layer. Apart from these layers, it may comprise still further layers, for example in each case one or more hole injection layers, hole transport layers, hole blocker layers, electron transport layers, electron injection layers, exciton blocker layers, electron blocker layers, charge generation layers and/or organic or inorganic p/n junctions. At the same time, it is possible that one or more hole transport layers are p-doped, for example with metal oxides such as MoO₃ or WO₃ or with (per)fluorinated electron-deficient aromatic systems, and/or that one or more electron transport layers are n-doped. It is likewise possible for interlayers to be introduced between two emitting layers, these having, for example, an exciton-blocking function and/or controlling the charge balance in the electroluminescent device. However, it should be pointed out that not necessarily every one of these layers need be present.

In this case, it is possible for the organic electroluminescent device to contain an emitting layer, or for it to contain a plurality of emitting layers. If a plurality of emission layers are present, these preferably have several emission maxima between 380 nm and 750 nm overall, such that the overall result is white emission; in other words, various emitting compounds which may fluoresce or phosphoresce are used in the emitting layers. Three-layer systems are especially preferred, where the three layers exhibit blue, green and orange or red emission, or systems having more than three emitting layers. Preference is further given to tandem OLEDs. The system may also be a hybrid system wherein one or more layers fluoresce and one or more other layers phosphoresce. White-emitting organic electroluminescent devices may be used for lighting applications or else with color filters for full-color displays.

In a preferred embodiment of the invention, the organic electroluminescent device comprises the metal complex of the invention as emitting compound in one or more emitting layers.

When the metal complex of the invention is used as emitting compound in an emitting layer, it is preferably used in combination with one or more matrix materials. The mixture of the metal complex of the invention and the matrix material contains between 0.1% and 99% by weight, preferably between 1% and 90% by weight, more preferably between 3% and 40% by weight and especially between 5% and 25% by weight of the metal complex of the invention, based on the overall mixture of emitter and matrix material. Correspondingly, the mixture contains between 99.9% and 1% by weight, preferably between 99% and 10% by weight, more preferably between 97% and 60% by weight and especially between 95% and 75% by weight of the matrix material, based on the overall mixture of emitter and matrix material.

The matrix material used may generally be any materials which are known for the purpose according to the prior art. The triplet level of the matrix material is preferably higher than the triplet level of the emitter.

Suitable matrix materials for the compounds of the invention are ketones, phosphine oxides, sulfoxides and sulfones, for example according to WO 2004/013080, WO 2004/093207, WO 2006/005627 or WO 2010/006680, triarylamines, carbazole derivatives, e.g. CBP (N,N-biscarbazolylbiphenyl), m-CBP or the carbazole derivatives disclosed in WO 2005/039246, US 2005/0069729, JP 2004/288381, EP 1205527, WO 2008/086851 or US 2009/0134784, biscarbazole derivatives, indolocarbazole derivatives, for example according to WO 2007/063754 or WO 2008/056746, indenocarbazole derivatives, for example according to WO 2010/136109 or WO 2011/000455, azacarbazoles, for example according to EP 1617710, EP 1617711, EP 1731584, JP 2005/347160, bipolar matrix materials, for example according to WO 2007/137725, silanes, for example according to WO 2005/111172, azaboroles or boronic esters, for example according to WO 2006/117052, diazasilole derivatives, for example according to WO 2010/054729, diazaphosphole derivatives, for example according to WO 2010/054730, triazine derivatives, for example according to WO 2010/015306, WO 2007/063754 or WO 2008/056746, zinc complexes, for example according to EP 652273 or WO 2009/062578, dibenzofuran derivatives, for example according to WO 2009/148015 or WO 2015/169412, or bridged carbazole derivatives, for example according to US 2009/0136779, WO 2010/050778, WO 2011/042107 or WO 2011/088877.

It may also be preferable to use a plurality of different matrix materials as a mixture, especially at least one electron-conducting matrix material and at least one hole-conducting matrix material. A preferred combination is, for example, the use of an aromatic ketone, a triazine derivative or a phosphine oxide derivative with a triarylamine derivative or a carbazole derivative, especially a biscarbazole derivative, as mixed matrix for the compound of the invention. Preference is likewise given to the use of a mixture of a charge-transporting matrix material and an electrically inert matrix material having no significant involvement, if any, in the charge transport, as described, for example, in WO 2010/108579. Preference is likewise given to the use of two electron-transporting matrix materials, for example triazine derivatives and lactam derivatives, as described, for example, in WO 2014/094964.

Depicted below are examples of compounds that are suitable as matrix materials for the compounds of the invention.

Examples of triazines and pyrimidines which can be used as electron-transporting matrix materials are the following compounds:

Examples of lactams which can be used as electron-transporting matrix materials are the following compounds:

Examples of ketones which can be used as electron-transporting matrix materials are the following compounds:

Examples of metal complexes which can be used as electron-transporting matrix materials are the following compounds:

Examples of phosphine oxides which can be used as electron-transporting matrix materials are the following compounds:

Examples of indolo- and indenocarbazole derivatives in the broadest sense which can be used as hole- or electron-transporting matrix materials according to the substitution pattern are the following compounds:

Examples of carbazole derivatives which can be used as hole- or electron-transporting matrix materials according to the substitution pattern are the following compounds:

Examples of bridged carbazole derivatives which can be used as hole-transporting matrix materials are the following compounds:

Examples of biscarbazoles which can be used as hole-transporting matrix materials are the following compounds:

Examples of amines which can be used as hole-transporting matrix materials are the following compounds:

Examples of materials which can be used as wide bandgap matrix materials are the following compounds:

It is further preferable to use a mixture of two or more triplet emitters together with a matrix. In this case, the triplet emitter having the shorter-wave emission spectrum serves as co-matrix for the triplet emitter having the longer-wave emission spectrum. For example, it is possible to use the metal complexes of the invention as co-matrix for longer-wave-emitting triplet emitters, for example for green- or red-emitting triplet emitters. In this case, it may also be preferable when both the shorter-wave- and the longer-wave-emitting metal complex is a complex is a compound of the invention. Suitable compounds for this purpose are especially also those disclosed in WO 2016/124304 and WO 2017/032439.

Examples of suitable triplet emitters that may be used as co-dopants for the compounds of the invention are depicted in the table below.

The metal complexes of the invention can also be used in other functions in the electronic device, for example as hole transport material in a hole injection or transport layer, as charge generation material, as electron blocker material, as hole blocker material or as electron transport material, for example in an electron transport layer, according to the exact structure of the ligand. It is likewise possible to use the metal complexes of the invention as matrix material for other phosphorescent metal complexes in an emitting layer.

Preferred cathodes are metals having a low work function, metal alloys or multilayer structures composed of various metals, for example alkaline earth metals, alkali metals, main group metals or lanthanoids (e.g. Ca, Ba, Mg, Al, In, Mg, Yb, Sm, etc.). Additionally suitable are alloys composed of an alkali metal or alkaline earth metal and silver, for example an alloy composed of magnesium and silver. In the case of multilayer structures, in addition to the metals mentioned, it is also possible to use further metals having a relatively high work function, for example Ag, in which case combinations of the metals such as Mg/Ag, Ca/Ag or Ba/Ag, for example, are generally used. It may also be preferable to introduce a thin interlayer of a material having a high dielectric constant between a metallic cathode and the organic semiconductor. Examples of useful materials for this purpose are alkali metal or alkaline earth metal fluorides, but also the corresponding oxides or carbonates (e.g. LiF, Li₂O, BaF₂, MgO, NaF, CsF, Cs₂CO₃, etc.). Likewise useful for this purpose are organic alkali metal complexes, e.g. Liq (lithium quinolinate). The layer thickness of this layer is preferably between 0.5 and 5 nm.

Preferred anodes are materials having a high work function. Preferably, the anode has a work function of greater than 4.5 eV versus vacuum.

Firstly, metals having a high redox potential are suitable for this purpose, for example Ag, Pt or Au. Secondly, metal/metal oxide electrodes (e.g. Al/Ni/NiOx, Al/PtOx) may also be preferred. For some applications, at least one of the electrodes has to be transparent or partly transparent in order to enable either the irradiation of the organic material (O-SC) or the emission of light (OLED/PLED, O-LASER). Preferred anode materials here are conductive mixed metal oxides. Particular preference is given to indium tin oxide (ITO) or indium zinc oxide (IZO). Preference is further given to conductive doped organic materials, especially conductive doped polymers, for example PEDOT, PANI or derivatives of these polymers. It is further preferable when a p-doped hole transport material is applied to the anode as hole injection layer, in which case suitable p-dopants are metal oxides, for example MoO₃ or WO₃, or (per)fluorinated electron-deficient aromatic systems. Further suitable p-dopants are HAT-CN (hexacyanohexaazatriphenylene) or the compound NPD9 from Novaled. Such a layer simplifies hole injection into materials having a low HOMO, i.e. a large HOMO in terms of magnitude.

In the further layers, it is generally possible to use any materials as used according to the prior art for the layers, and the person skilled in the art is able, without exercising inventive skill, to combine any of these materials with the materials of the invention in an electronic device.

The device is correspondingly (according to the application) structured, contact-connected and finally hermetically sealed, since the lifetime of such devices is severely shortened in the presence of water and/or air.

Additionally preferred is an organic electroluminescent device, characterized in that one or more layers are coated by a sublimation process. In this case, the materials are applied by vapor deposition in vacuum sublimation systems at an initial pressure of typically less than 10⁻⁵ mbar, preferably less than 10⁻⁶ mbar. It is also possible that the initial pressure is even lower or even higher, for example less than 10⁻⁷ mbar.

Preference is likewise given to an organic electroluminescent device, characterized in that one or more layers are coated by the OVPD (organic vapor phase deposition) method or with the aid of a carrier gas sublimation. In this case, the materials are applied at a pressure between 10⁻⁵ mbar and 1 bar. A special case of this method is the OVJP (organic vapor jet printing) method, in which the materials are applied directly by a nozzle and thus structured.

Preference is additionally given to an organic electroluminescent device, characterized in that one or more layers are produced from solution, for example by spin-coating, or by any printing method, for example screen printing, flexographic printing, offset printing or nozzle printing, but more preferably LITI (light-induced thermal imaging, thermal transfer printing) or inkjet printing. For this purpose, soluble compounds are needed, which are obtained, for example, through suitable substitution. In a preferred embodiment of the invention, the layer comprising the compound of the invention is applied from solution.

The organic electroluminescent device can also be produced as a hybrid system by applying one or more layers from solution and applying one or more other layers by vapor deposition. For example, it is possible to apply an emitting layer comprising a metal complex of the invention and a matrix material from solution, and to apply a hole blocker layer and/or an electron transport layer thereto by vapor deposition under reduced pressure.

These methods are known in general terms to those skilled in the art and can be applied by those skilled in the art without difficulty to organic electroluminescent devices comprising compounds of formula (1) or the above-detailed preferred embodiments.

The electronic devices of the invention, especially organic electroluminescent devices, are notable for one or more of the following surprising advantages over the prior art:

-   1. The compounds of the invention have a very high photoluminescence     quantum yield. When used in an organic electroluminescent device,     this leads to excellent efficiencies. -   2. The compounds of the invention have a very short luminescence     lifetime. When used in an organic electroluminescent device, this     leads to improved roll-off characteristics, and also, through     avoidance of non-radiative relaxation channels, to a higher     luminescence quantum yield.

These abovementioned advantages are not accompanied by a deterioration in the further electronic properties.

The invention is illustrated in more detail by the examples which follow, without any intention of restricting it thereby. The person skilled in the art will be able to use the details given, without exercising inventive skill, to produce further electronic devices of the invention and hence to execute the invention over the entire scope claimed.

EXAMPLES

The syntheses which follow, unless stated otherwise, are conducted under a protective gas atmosphere in dried solvents. The metal complexes are additionally handled with exclusion of light or under yellow light. The solvents and reagents can be purchased, for example, from Sigma-ALDRICH or ABCR. The respective figures in square brackets or the numbers quoted for individual compounds relate to the CAS numbers of the compounds known from the literature.

A: Synthesis of the Synthons

Example B1

A mixture of 23.0 g (100 mmol) of 2-(4-chlorophenyl)-2H-benzo-[d]-[1,2,3]-triazole [3933-77-5], 27.4 g (107 mmol) of bis(pinacolato)diborane [73183-34-3], 29.5 g (300 mmol) of potassium acetate, 1.1 g (4 mmol) of SPhos [657408-07-6], 650 mg (3 mmol) of palladium(II) acetate and 450 ml of 1,4-dioxane is heated under reflux for 16 h. The dioxane is removed on a rotary evaporator, the black residue is worked up by extraction with 1000 ml of ethyl acetate and 500 ml of water in a separating funnel, and the organic phase is washed once with 300 ml of water and once with 150 ml of saturated sodium chloride solution and filtered through a silica gel bed. The silica gel is washed with 2×250 ml of ethyl acetate. The filtrate is dried over sodium sulfate and then concentrated. The residue is digested in 200 ml of n-heptane and the suspension is heated to reflux for 1 h. After cooling, the solids are filtered off with suction and washed with a little n-heptane. Yield: 26.0 g (81 mmol), 81%. Purity: about 96% by ¹H NMR.

Example B2

Procedure analogous to example B1, except using 5-chloro-2-(1H-pyrrol-1-yl)pyrimidine [860785-43-9] rather than 2-(4-chlorophenyl)-2H-benzo-[d]-[1,2,3]-triazole.

Example B3

A mixture of 10 g (50 mmol) of [4-(2-pyrimidinyl)phenyl]boronic acid [1615248-01-5], 18.1 g (50 mmol) of 1,3-dibromo-2-iodobenzene [19821-80-8], 15.9 g (150 mmol) of sodium carbonate, 390 mg (1.5 mmol) of triphenylphosphine, 110 mg (0.5 mmol) of palladium(II) acetate, 120 ml of toluene, 40 ml of ethanol and 120 ml of water is heated under reflux for 60 h. After cooling, the reaction mixture is worked up by extraction in a separating funnel. For this purpose, the organic phase is removed and the aqueous phase is extracted twice with 50 ml each time of ethyl acetate. Subsequently, the combined organic phases are washed twice with 100 ml each time of water and once with 50 ml of saturated sodium chloride solution, dried over sodium sulfate and concentrated to dryness. The residue is purified by column chromatography on silica gel with dichloromethane as eluent. Yield 8.1 g (21 mmol), 42%, 95% pure by ¹H NMR.

Example B160

A mixture of 10 g (50 mmol) of [4-(2-pyrimidinyl)phenyl]boronic acid [1615248-01-5], 11.3 g (50 mmol) of 1,3-dichloro-2-bromobenzene [19393-92-1], 15.9 g (150 mmol) of sodium carbonate, 1.2 g (1 mmol) of tetrakis(triphenylphosphine)palladium(0), 200 ml of 1,2-dimethoxyethane and 200 ml of water is heated under reflux for 20 h. After cooling, the reaction mixture is worked up by extraction in a separating funnel with 150 ml of toluene and 150 ml of water. The organic phase is removed and the aqueous phase is extracted twice with 50 ml each time of toluene. Subsequently, the combined organic phases are washed twice with 100 ml each time of water and once with 50 ml of saturated sodium chloride solution, dried over sodium sulfate and concentrated to dryness. The residue is purified by column chromatography on silica gel with ethyl acetate/heptane. A colorless oil is obtained. Yield: 10.5 g (35 mmol), 70%, 97% pure by ¹H NMR.

The following compounds can be prepared in an analogous manner:

Ex. Reactant Product Yield B4

65% B5

71% B6 B1

69% B7 B2

72%

Example B8

A mixture of 18.1 g (100 mmol) of 6-chlorotetralone [26673-31-4], 16.5 g (300 mmol) of propargylamine [2450-71-7], 796 mg [2 mmol] of sodium tetrachloroaurate(III) dihydrate and 200 ml of ethanol is stirred in an autoclave at 120° C. for 24 h. After cooling, the ethanol is removed under reduced pressure, the residue is taken up in 200 ml of ethyl acetate, the solution is washed three times with 200 ml of water and once with 100 ml of saturated sodium chloride solution and dried over magnesium sulfate, and then the latter is filtered off using a silica gel bed in the form of a slurry. After the ethyl acetate has been removed under reduced pressure, the residue is chromatographed on silica gel with n-heptane/ethyl acetate (1:2 v/v). Yield: 9.7 g (45 mmol), 45%. Purity: about 98% by ¹H NMR.

Example B9

A mixture of 25.1 g (100 mmol) of 2,5-dibromo-4-methylpyridine [3430-26-0], 15.6 g (100 mmol) of 4-chlorophenylboronic acid [1679-18-1], 27.6 g (200 mmol) of potassium carbonate, 1.57 g (6 mmol) of triphenylphosphine [603-35-0], 676 mg (3 mmol) of palladium(II) acetate [3375-31-3], 200 g of glass beads (diameter 3 mm), 200 ml of acetonitrile and 100 ml of ethanol is heated under reflux for 48 h. After cooling, the solvents are removed under reduced pressure, 500 ml of toluene are added, the mixture is washed twice with 300 ml each time of water and once with 200 ml of saturated sodium chloride solution, dried over magnesium sulfate and filtered through a silica gel bed in the form of a slurry, which is washed with 300 ml of toluene. After the toluene has been removed under reduced pressure, it is recrystallized once from methanol/ethanol (1:1 v/v) and once from n-heptane. Yield: 17.3 g (61 mmol), 61%. Purity: about 95%. ¹H NMR.

Example B10

B10 can be prepared analogously to the procedure in example B9. For this purpose, 4-bromo-6-tert-butylpyrimidine [19136-36-8] is used rather than 2,5-dibromo-4-methylpyridine. Yield: 70%.

Example B11

A mixture of 28.3 g (100 mmol) of B9, 12.8 g (105 mmol) of phenylboronic acid, 31.8 g (300 mmol) of sodium carbonate, 787 mg (3 mmol) of triphenylphosphine, 225 mg (1 mmol) of palladium(II) acetate, 300 ml of toluene, 150 ml of ethanol and 300 ml of water is heated under reflux for 48 h. After cooling, the mixture is extended with 300 ml of toluene, and the organic phase is removed, washed once with 300 ml of water and once with 200 ml of saturated sodium chloride solution, and dried over magnesium sulfate. After the solvent has been removed, the residue is chromatographed on silica gel (toluene/ethyl acetate, 9:1 v/v). Yield: 17.1 g (61 mmol), 61%. Purity: about 97% by ¹H NMR.

In an analogous manner, it is possible to synthesize the following compounds:

Ex. Boronic ester Product Yield B12

56% B13

61% B14

55%

Example B15

A mixture of 164.2 g (500 mmol) of 2-(1,1,2,2,3,3-hexamethylindan-5-yl)-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane [152418-16-9] (boronic acids can be used analogously), 142.0 g (500 mmol) of 5-bromo-2-iodopyridine [223463-13-6], 159.0 g (1.5 mol) of sodium carbonate, 5.8 g (5 mmol) of tetrakis(triphenylphosphino)palladium(0), 700 ml of toluene, 300 ml of ethanol and 700 ml of water is heated under reflux with good stirring for 16 h. After cooling, 1000 ml of toluene are added, the organic phase is removed and the aqueous phase is re-extracted with 300 ml of toluene. The combined organic phases are washed once with 500 ml of saturated sodium chloride solution. After the organic phase has been dried over sodium sulfate and the solvent has been removed under reduced pressure, the crude product is recrystallized twice from about 300 ml of EtOH. Yield: 130.8 g (365 mmol), 73%. Purity: about 95% by ¹H NMR.

It is analogously possible to prepare the compounds which follow, generally using 5-bromo-2-iodopyridine ([223463-13-6]) as pyridine derivative, which is not listed separately in the table which follows. Only different pyridine derivatives are listed explicitly in the table. Recrystallization can be accomplished using solvents such as ethyl acetate, cyclohexane, toluene, acetonitrile, n-heptane, ethanol or methanol. It is also possible to use these solvents for hot extraction, or to purify by chromatography on silica gel in an automated column system (Torrent from Axel Semrau).

Boronic acid/ester Ex. Pyridine Product Yield B16

  [100124-06-9]

69% B17

  [402936-15-6]

71% B18

  [169126-63-0]

78% B19

  [1801624-61-2]

78% B20

  See WO 2016/124304

81% B21

  [98-80-6]/[1381937-40-1]

73% B22

  [1609374-04-0]

68% B23

  [1174312-53-8]

63%

Example B24

Variant A:

A mixture of 35.8 g (100 mmol) of B15, 25.4 g (100 mmol) of bis(pinacolato)diborane [73183-34-3], 49.1 g (500 mmol) of potassium acetate, 1.5 g (2 mmol) of 1,1-bis(diphenylphosphino)ferrocenedichloropalladium(II) complex with DCM [95464-05-4], 200 g of glass beads (diameter 3 mm), 700 ml of 1,4-dioxane and 700 ml of toluene is heated under reflux for 16 h. After cooling, the suspension is filtered through a Celite bed and the solvent is removed under reduced pressure. The black residue is digested with 1000 ml of hot n-heptane, cyclohexane or toluene and filtered through a Celite bed while still hot, and then concentrated to about 200 ml, in the course of which the product begins to crystallize. Alternatively, hot extraction with ethyl acetate is possible. The crystallization is completed in a refrigerator overnight, and the crystals are filtered off and washed with a little n-heptane. A second product fraction can be obtained from the mother liquor. Yield: 31.6 g (78 mmol), 78%. Purity: about 95% by ¹H NMR.

Variant B: Conversion of Aryl Chlorides

As variant A, except that, rather than 1,1-bis(diphenylphosphino)-ferrocenedichloropalladium(II) complex with DCM, 2 mmol of SPhos [657408-07-6] and 1 mmol of palladium(II) acetate are used.

In an analogous manner, it is possible to prepare the following compounds, and it is also possible to use cyclohexane, toluene, acetonitrile or mixtures of said solvents for purification rather than n-heptane:

Bromide-Variant A Ex. Chloride-Variant B Product Yield B25

  [27012-25-5]

85% B26

  [1215073-34-9]

80% B27

  [1035556-84-3]

83% B28

  [1486482-87-4]

77% B29

  B16

67% B30

  B17

70% B31

  B18

80% B32

  B19

80% B33

  B20

78% B34

  [31686-64-3]

74% B35

  B21

70% B36

  [88345-95-3]

68% B37

  [22960-25-4]

76% B38

  [57669-37-1]

83% B39

  [68473-51-8]

85% B40

55% B14 B41

  [463336-07-4]

72% B42

  [1039080-00-6]

78% B43

  [1492036-00-6]

82% B44

  B21

60% B45

  B23

75% B46

  [1246851-70-6]

88% B47

  [60781-85-3]

78% B48

  [1338923-08-2]

82% B49

  [1446208-20-3]

80% B50

85% B10 B51

88% B8 B52

76% [102200-03-3] B53

81% B11 B54

78% B12 B55

75% B13

Example B56

A mixture of 28.1 g (100 mmol) of B25, 28.2 g (100 mmol) of 1-bromo-2-iodobenzene [583-55-1], 31.8 g (300 mmol) of sodium carbonate, 787 mg (3 mmol) of triphenylphosphine, 225 mg (1 mmol) of palladium(II) acetate, 300 ml of toluene, 150 ml of ethanol and 300 ml of water is heated under reflux for 24 h. After cooling, the mixture is extended with 500 ml of toluene, and the organic phase is removed, washed once with 500 ml of water and once with 500 ml of saturated sodium chloride solution and dried over magnesium sulfate. After the solvent has been removed, the residue is recrystallized from ethyl acetate/n-heptane or chromatographed on silica gel (toluene/ethyl acetate, 9:1 v/v). Yield: 22.7 g (73 mmol), 73%. Purity: about 97% by ¹H NMR.

The compounds which follow can be prepared in an analogous manner, and recrystallization can be accomplished using solvents such as ethyl acetate, cyclohexane, toluene, acetonitrile, n-heptane, ethanol or methanol, for example. It is also possible to use these solvents for hot extraction, or to purify by chromatography on silica gel in an automated column system (Torrent from Axel Semrau).

Ex. Boronic ester Product Yield B57

56% B58

72% B59

71% B60

70% B61

69% B62

67% B63

63% B64

70% B65

73% B66

72% B67

48% B68

65% B69

65% B70

68% B71

77% B72

70% B73

66% B74

71% B75

64% B76

58% B77

62% B78

75% B79

78% B80

82%

Example B81

A mixture of 36.4 g (100 mmol) of 2,2′-(5-chloro-1,3-phenylene)bis[4,4,5,5-tetramethyl-1,3,2-dioxaborolane] [1417036-49-7], 65.2 g (210 mmol) of B56, 42.4 g (400 mmol) of sodium carbonate, 1.57 g (6 mmol) of triphenylphosphine, 500 mg (2 mmol) of palladium(II) acetate, 500 ml of toluene, 200 ml of ethanol and 500 ml of water is heated under reflux for 48 h. After cooling, the mixture is extended with 500 ml of toluene, and the organic phase is removed, washed once with 500 ml of water and once with 500 ml of saturated sodium chloride solution and dried over magnesium sulfate. After the solvent has been removed, the residue is chromatographed on silica gel (n-heptane/ethyl acetate, 2:1 v/v). Yield: 41.4 g (68 mmol), 68%. Purity: about 95% by ¹H NMR.

The compounds which follow can be prepared in an analogous manner, and recrystallization can be accomplished using solvents such as ethyl acetate, cyclohexane, toluene, acetonitrile, n-heptane, ethanol or methanol, for example. It is also possible to use these solvents for hot extraction, or to purify by chromatography on silica gel in an automated column system (Torrent from Axel Semrau).

Ex. Bromide Product Yield B82

67% B83

62% B84

55% B85

63% B86

60% B87

61% B88

58% B89

56% B90

60% B91

64% B92

60% B200

67%

Example B93

A mixture of 17.1 g (100 mmol) of 4-(2-pyridyl)phenol [51035-40-6] and 12.9 g (100 mmol) of diisopropylethylamine [7087-68-5] is stirred in 400 ml of dichloromethane at room temperature for 10 min. 6.2 ml (40 mmol) of 5-chloroisophthaloyl chloride [2855-02-9], dissolved in 30 ml of dichloromethane, are added dropwise, and the reaction mixture is stirred at room temperature for 14 h. Subsequently, 10 ml of water are added dropwise and the reaction mixture is transferred into a separating funnel. The organic phase is washed twice with 100 ml of water and once with 50 ml of saturated NaCl solution, dried over sodium sulfate and concentrated to dryness. Yield: 18.0 g (38 mmol), 95%. Purity: about 95% by ¹H NMR.

The following compounds can be prepared in an analogous manner: The molar amounts of the reactants used are specified if they differ from those as described in the procedure for B93.

Alcohol or amine Acid chloride Ex. Reaction time Product Yield B94

90% B95

96% B96

88% B97

76% B98

80% B99

73% B100

78%

Example B101

2.0 g (50 mmol) of sodium hydride (60% dispersion in paraffin oil) [7646-69-7] are suspended in 300 ml of THF, then 5.0 g (10 mmol) of B95 are added, and the suspension is stirred at room temperature for 30 minutes. Subsequently, 1.2 ml of iodomethane (50 mmol) [74-88-4] are added and the reaction mixture is stirred at room temperature for 50 h. 20 ml of conc. ammonia solution are added, the mixture is stirred for a further 30 minutes, and the solvent is largely drawn off under reduced pressure. The residue is taken up in 300 ml of dichloromethane, washed once with 200 ml of 5% by weight aqueous ammonia, twice with 100 ml each time of water and once with 100 ml of saturated sodium chloride solution, and dried over magnesium sulfate. The dichloromethane is removed under reduced pressure and the crude product is recrystallized from ethyl acetate/methanol. Yield: 4.3 g (8 mmol), 80%. Purity: about 98% by ¹H NMR.

In an analogous manner, it is possible to prepare the following compounds:

Ex. Reactant Product Yield B102

70% B103

69% B104

72%

Example B105

A mixture of 36.4 g (100 mmol) of 2,2′-(5-chloro-1,3-phenylene)bis[4,4,5,5-tetramethyl-1,3,2-dioxaborolane] [1417036-49-7], 70.6 g (210 mmol) of B69, 42.4 g (400 mmol) of sodium carbonate, 2.3 g (2 mmol) of tetrakis(triphenylphosphine)palladium(0), 1000 ml of 1,2-dimethoxyethane and 500 ml of water is heated under reflux for 48 h. After cooling, the precipitated solids are filtered off with suction and washed twice with 20 ml of ethanol. The solids are dissolved in 500 ml of dichloromethane and filtered through a Celite bed. The filtrate is concentrated down to 100 ml, then 400 ml of ethanol are added and the precipitated solids are filtered off with suction. The crude product is recrystallized once from ethyl acetate. Yield: 43.6 g (70 mmol), 70%. Purity: about 96% by ¹H NMR.

The compounds which follow can be prepared in an analogous manner, and recrystallization can be accomplished using solvents such as ethyl acetate, cyclohexane, toluene, acetonitrile, n-heptane, ethanol or methanol, for example. It is also possible to use these solvents for hot extraction, or to purify by chromatography on silica gel in an automated column system (Torrent from Axel Semrau).

B106

  B68

64% B107

  B70

54% B108

  B72

75% B109

  B73

71% B110

  B74

58% B111

  B75

60% B112

  B76

66% B113

  B77

70% B114

  B78

70% B115

  B79

63% B116

  B71

60% B117

  B80

61% B152

  [1989597-40-1]

57% B153

  [1989597-41-2]

60% B154

  [1989597-56-9]

66% B155

  [1989597-54-7]

62%

Example B119

A mixture of 57.1 g (100 mmol) of B81, 25.4 g (100 mmol) of bis(pinacolato)diborane [73183-34-3], 49.1 g (500 mmol) of potassium acetate, 2 mmol of SPhos [657408-07-6], 1 mmol of palladium(II) acetate, 200 g of glass beads (diameter 3 mm) and 700 ml of 1,4-dioxane is heated to reflux for 16 h while stirring. After cooling, the suspension is filtered through a Celite bed and the solvent is removed under reduced pressure. The black residue is digested with 1000 ml of hot ethyl acetate and filtered through a Celite bed while still hot, then concentrated to about 200 ml, in the course of which the product begins to crystallize. The crystallization is completed in a refrigerator overnight, and the crystals are filtered off and washed with a little ethyl acetate. A second product fraction can be obtained from the mother liquor. Yield: 31.6 g (78 mmol), 78%. Purity: about 95% by ¹H NMR.

The following compounds can be prepared in an analogous manner, and it is also possible to use toluene, n-heptane, cyclohexane or acetonitrile rather than ethyl acetate for recrystallization or for hot extraction in the case of sparingly soluble products:

Ex. Bromide Product Yield B120

80% B121

84% B122

71% B123

80% B124

85% B125

82% B126

77% B127

72% B128

77% B129

80% B130

81% B131

88% B132

79% B133

76% B134

89% B135

84% B136

79% B137

75% B138

77% B139

80% B140

82% B141

88% B142

90% B143

76% B144

80% B145

81% B146

84% B147

74% B148

73% B149

76% B150

72% B151

75% B156

70% B157

72% B158

69% B159

74% B120

69% B: Synthesis of the Ligands L and Ligand Precursors LV:

Example L1

Variant A:

A mixture of 5.9 g (15 mmol) of B3, 19.9 g (30.0 mmol) of B120, 9.2 g (87 mmol) of sodium carbonate, 340 mg (1.3 mmol) of triphenylphosphine, 98 mg (0.44 mmol) of palladium(II) acetate, 200 ml of toluene, 100 ml of ethanol and 200 ml of water is heated under reflux for 40 h. After cooling, the precipitated solids are filtered off with suction and washed twice with 30 ml each time of ethanol. The crude product is dissolved in 300 ml of dichloromethane and filtered through a silica gel bed. The silica gel bed is washed through three times with 200 ml each time of dichloromethane/ethyl acetate 1:1. The filtrate is washed twice with water and once with saturated sodium chloride solution and dried over sodium sulfate. The filtrate is concentrated to dryness. The residue is recrystallized from ethyl acetate at reflux. Yield: 8.8 g (10.7 mmol), 55%. Purity: about 99% by ¹H NMR.

Variant B:

A mixture of 4.5 g (15 mmol) of B160, 19.9 g (30.0 mmol) of B120, 13.8 g (87 mmol) of potassium phosphate monohydrate, 507 mg (0.6 mmol) of XPhos palladacycle Gen. 3 [1445085-55-1], 200 ml of THF and 100 ml of water is heated under reflux for 20 h. After cooling, the precipitated solids are filtered off with suction and washed with twice with 30 ml each time of water and twice with 30 ml each time of ethanol. The crude product is dissolved in 200 ml of dichloromethane and filtered through a silica gel bed. The silica gel bed is washed through three times with 200 ml each time of dichloromethane/ethyl acetate 1:1. The filtrate is washed twice with water and once with saturated sodium chloride solution, dried over sodium sulfate and concentrated to dryness. The residue is recrystallized from ethyl acetate at reflux. Yield: 12.0 g (9.2 mmol), 61%. Purity: about 99% by ¹H NMR.

The compounds which follow can be prepared analogously to the procedure described for L1 (variant B). In this case, it is also possible to use toluene, cyclohexane, ethyl acetate or dimethylformamide for purification by recrystallization or hot extraction. Alternatively, the ligands can be purified by chromatography.

Reac- Ex. tants Product Yield L2  B160 + B119

64% L3  B160 + B123

61% L4  B160 + B139

68% L5  B160 + B149

65% L6  B160 + B138

66% L7  B160 + B127

70% L8  B160 + B136

57% L9  B160 + B140

69% L10 B160 + B129

64% L11 B160 + B125

62% L12 B160 + B126

63% L13 B160 + B128

61% L14 B160 + B142

67% L15  B4 + B119

60% L16  B4 + B120

58% L17  B4 + B127

56% L18  B4 + B131

53% L19  B4 + B146

70% L20  B4 + B147

58% L21  B4 + B122

63% L22  B4 + B150

57% L23  B4 + B131

56% L24  B4 + B145

65% L25  64 + B148

60% L26  B5 + B119

60% L27  B5 + B120

58% L28  B5 + B143

62% L29  B5 + B129

57% L30  B5 + B144

63% L31  B6 + B120

65% L32  B6 + B143

61% L33  B6 + B129

55% L34  B6 + B119

60% L35  B7 + B119

62% L36  B7 + B128

57% L37  B7 + B131

50% L38  B7 + B150

63% L39  B160 + B130

58% L40 B160 + B156

55% L41 B160 + B157

58% L42 B160 + B158

60% L43 B160 + B159

59% L44 B160 + 15 mmol B123 + 15 mmol B139

20% Chromatographic separation of the mixture on an automated column system (Torrent from A. Semrau) with isolation of the unsymmetric ligand L45 B160 + 15 mmol B120 + 15 mmol B156

22% Chromatographic separation of the mixture on an automated column system (Torrent from A. Semrau) with isolation of the unsymmetric ligand  LV100 B160 + B210

68%

Example LV110

Analogous to F. Diness et al., Angew. Chem. Int. Ed., 2012, 51, 8012. A mixture of 21.3 g (20 mmol) of LV1, 11.8 g (100 mmol) of benzimidazole and 97.9 g (300 mmol) of cesium carbonate in 500 ml of N,N-dimethylacetamide is heated to 175° C. in a stirred autoclave for 18 h. After cooling, the solvent is largely drawn off and the residue is taken up in 500 ml of toluene, washed three times with 300 ml each time of water and once with 300 ml of saturated sodium chloride solution, dried over magnesium sulfate and then filtered through a Celite bed in the form of a slurry. After the solvent has been removed under reduced pressure, the residue is recrystallized from ethyl acetate/methanol. Yield: 16.0 g (11 mmol), 55%. Purity: about 96% by ¹H NMR.

In an analogous manner, it is possible to synthesize the following compounds:

Ex. Reactants Product Yield LV111

51% LV112

57% LV113

60%

Example LV120

To a solution of 14.6 g (10 mmol) of LV110 in 100 ml of DCM are added dropwise 2.8 ml (44 mmol) of methyl iodide [74-88-4] and the mixture is heated to 60° C. in a stirred autoclave for 24 h. After cooling, the solvent and excess methyl iodide are drawn off under reduced pressure. The ligand precursor thus obtained is converted without further purification. Yield: 20.3 g (10 mmol), quantitative. Purity: about 95% by ¹H NMR.

In an analogous manner, it is possible to synthesize the following compounds:

Product Ex. Reactant Yield LV121

quant. LV111 LV122

quant. LV112 LV123

quant. LV113

Example LV130

A mixture of 14.6 g (10 mmol) of LV110, 16.6 g (45 mmol) of diphenyliodonium tetrafluoroborate [313-39-3], 363 mg (2 mmol) of copper(II) acetate [142-71-2] in 200 ml of DMF is heated to 100° C. for 8 h. After cooling, the solvent is removed under reduced pressure, the residue is taken up in a mixture of 100 ml of dichloromethane, 100 ml of acetone and 20 ml of methanol and filtered through a silica gel bed, and the core fraction is extracted and concentrated to dryness. The ligand precursor thus obtained is converted without further purification. Yield: 14.8 g (7 mmol), 70%. Purity: about 90% by ¹H NMR.

In an analogous manner, it is possible to synthesize the following compounds:

Product Ex. Reactant Yield LV131

65% LV111 LV132

68% LV112 LV133

63% LV113 C: Synthesis of the Metal Complexes: Variant A:

Example Ir₂(L1)

A mixture of 13.0 g (10 mmol) of ligand L1, 9.8 g (20 mmol) of trisacetylacetonatoiridium(III) [15635-87-7] and 100 g of hydroquinone [123-31-9] is initially charged in a 1000 ml two-neck round-bottom flask with a glass-sheathed magnetic bar. The flask is provided with a water separator (for media of lower density than water) and an air condenser with argon blanketing and placed into a metal heating bath. The apparatus is purged with argon from the top via the argon blanketing system for 15 min, allowing the argon to flow out of the side neck of the two-neck flask. Through the side neck of the two-neck flask, a glass-sheathed Pt-100 thermocouple is introduced into the flask and the end is positioned just above the magnetic stirrer bar. The apparatus is thermally insulated with several loose windings of domestic aluminum foil, the insulation being run up to the middle of the riser tube of the water separator. Then the apparatus is heated rapidly with a heated laboratory stirrer system to 250° C., measured with the Pt-100 thermal sensor which dips into the molten stirred reaction mixture. Over the next 2 h, the reaction mixture is kept at 250° C., in the course of which a small amount of condensate is distilled off and collects in the water separator. The reaction mixture is left to cool down to 190° C., then 100 ml of ethylene glycol are added dropwise. The mixture is left to cool down further to 80° C., then 500 ml of methanol are added dropwise and the mixture is heated at reflux for 1 h. The suspension thus obtained is filtered through a double-ended frit, and the solids are washed twice with 50 ml of methanol and dried under reduced pressure. The solids thus obtained are dissolved in 220 ml of dichloromethane and filtered through about 1 kg of silica gel in the form of a dichloromethane slurry (column diameter about 18 cm) with exclusion of air in the dark, leaving dark-colored components at the start. The core fraction is cut out and concentrated on a rotary evaporator, with simultaneous continuous dropwise addition of MeOH until crystallization. After removal with suction, washing with a little MeOH and drying under reduced pressure, further purification is effected by hot extraction five times with toluene (amount initially charged in each case about 150 ml, extraction thimble: standard Soxhlet thimbles made from cellulose from Whatman) with careful exclusion of air and light. Finally, the products are heat-treated at 280° C. under high vacuum. 10.8 g of red solid (6.4 mmol), 64%. Purity: >99.9% by HPLC.

The compounds which follow can be synthesized in an analogous manner. The metal complexes shown below can in principle be purified by chromatography, typically using an automated column system (Torrent from Axel Semrau), recrystallization or hot extraction (also abbreviated to HE in the table below). Residual solvents can be removed by heat treatment under high vacuum at typically 250-330° C.

In an analogous manner, it is possible to obtain mixed metallic Rh—Ir complexes by first using just 10 mmol rather than 20 mmol of tris(acetylacetonato)iridium(III) [15635-87-7] and then, after half the reaction time specified, adding 4.0 g (10 mmol) of tris(acetylacetonato)rhodium(III) [14284-92-5].

Variant B: Carbene Complexes

A suspension of 10 mmol of the carbene ligand precursor LV and 40 mmol of Ag₂O in 300 ml of dioxane is stirred at 30° C. for 12 h. Then 20 mmol of [Ir(COD)Cl]₂ [12112-67-3] are added and the mixture is heated under reflux for 8 h. The solids are filtered off while the mixture is still hot and they are washed three times with 50 ml each time of hot dioxane, and the filtrates are combined and concentrated to dryness under reduced pressure. The crude product thus obtained is chromatographed twice on basic alumina with ethyl acetate/cyclohexane or toluene. The product is purified further by continuous hot extraction five times with acetonitrile/dichloromethane and hot extraction twice with ethyl acetate/methanol (amount initially charged in each case about 200 ml, extraction thimble: standard Soxhlet thimbles made from cellulose from Whatman) with careful exclusion of air and light. Finally, the product is heat-treated under high vacuum. Purity: >99.8% by HPLC.

The compounds which follow can be prepared analogously to variants A and B

Ex. Reactant Product/reaction conditions/hot extractant (HE) Yield Variant A Rh₂(L1) L1 Rh(acac)₃ [14284- 92-5] rather than Ir(acac)₃

50% Rh₂(L1) 250° C.; 2 h Hot extraction: toluene Ir₂(L2) L2

60% Ir₂(L2) 250° C.; 4 h Hot extraction: ethyl acetate Rh₂(L2) L2 Rh(acac)₃ [14284- 92-5] rather than Ir(acac)

48% Rh₂(L2) 250° C.; 2 h Hot extraction: ethyl acetate Ir₂(L3) L3

56% Ir₂(L3) 250° C.: 3 h HE: ethyl acetate/acetonitrile 4:1 Ir₂(L4) L4

62% Ir₂(L4) 250° C.; 3 h HE: ethyl acetate/acetonitrile 2:1 Ir₂(L5) L5

52% Ir₂(L5) 250° C.; 2 h Recrystallization: DMF Ir₂(L6) L6

65% Ir₂(L6) 250° C.; 5 h Hot extraction: o-xylene Ir₂(L7) L7

60% Ir₂(L7) 250° C./5 h Hot extraction: toluene Ir₂(L8) L8

43% Ir₂(L8) 220° C.; 5 h Recrystallization: DMSO Ir₂(L9) L9

56% Ir₂(L9) 250° C.; 3 h Hot extraction: toluene Ir₂(L10) L10

58% Ir₂(L10) 250° C.; 1.5 h Hot extraction: ethyl acetate Ir₂(L11) L11

62% Ir₂(L11) 250° C.; 2 h Hot extraction: n-butyl acetate Ir₂(L12) L12

58% Ir₂(L12) 250° C.; 2 h Hot extraction: toluene Ir₂(L13) L13

61% Ir₂(L13) 250° C.; 3 h Hot extraction: n-butyl acetate Ir₂(L14) L14

57% Ir₂(L14) 260° C.; 3 h Hot extraction: o-xylene Ir₂(L15) L15

62% Ir₂(L15) 250° C.; 2 h Hot extraction: toluene Ir₂(L16) L16

56% Ir₂(L16) 250° C.; 2 h Hot extraction: ethyl acetate Ir₂(L17) L17

53% Ir₂(L17) 265° C.; 3 h Hot extraction: toluene Ir₂(L18) L18

41% Ir₂(L18) 255° C.; 2 h Recrystallization: DMF Ir₂(L19) L19

65% Ir₂(L19) 250° C.; 3 h Hot extraction: o-xylene Ir₂(L20) L20

50% Ir₂(L20) 250° C.; 3 h Hot extraction: cyclohexane Ir₂(L21) L21

55% Ir₂(L21) 250° C.; 3 h Hot extraction: toluene Ir₂(L22) L22

58% Ir₂(L22) 265° C.; 5 h Hot extraction: n-butyl acetate Ir₂(L23) L23

48% Ir₂(L23) 250° C.; 3 h Hot extraction: n-butyl acetate Ir₂(L24) L24

63% Ir₂(L24) 250° C.; 2 h Hot extraction: o-xylene Ir₂(L25) L25

54% Ir₂(L25) 250° C.; 2 h Hot extraction: ethyl acetate Ir₂(L26) L26

63% Ir₂(L26) 250° C.; 3.5 h Hot extraction: n-butyl acetate Ir₂(L27) L27

66% Ir₂(L27) 260° C.; 3 h Hot extraction: ethyl acetate Ir₂(L28) L28

56% Ir₂(L28) 250° C.; 3 h Hot extraction: n-butyl acetate Ir₂(L29) L29

60% Ir₂(L29) 235° C.; 2 h Hot extraction: toluene Ir₂(L30) L30

52% Ir₂(L30) 250° C.; 2 h Hot extraction: toluene Ir₂(L31) L31

48% Ir₂(L31) 240° C.; 2 h Hot extraction: dichloromethane Ir₂(L32) L32

46% Ir₂(L32) 230° C.; 2 h Hot extraction: toluene Ir₂(L33) L33

47% Ir₂(L33) 250° C.; 2 h Recrystallization: dimethylformamide Ir₂(L34) L34

50% Ir₂(L34) 250° C.; 3 h Hot extraction: n-butyl acetate Ir₂(L35) L35

43% Ir₂(L35) 270° C.; 3 h Hot extraction: toluene Ir₂(L36) L36

52% Ir₂(L36) 260° C.; 3 h Hot extraction: ethyl acetate Ir₂(L37) L37

41% Ir₂(L37) 250° C.; 4 h Hot extraction; 2-propanol Ir₂(L38) L38

44% Ir₂(L38) 250° C.; 3 h Hot extraction: ethyl acetate Ir₂(L39) L39

58% Ir₂(L39) 260° C.; 3 h Hot extraction: ethyl acetate Ir₂(L40) L40

55% Ir₂(L40) 260° C.; 3 h Hot extraction: ethyl acetate Ir₂(L41) L41

57% Ir₂(L41) 260° C.; 3 h Hot extraction: toluene Ir₂(L42) L42

51% Ir₂(L42) 260° C.; 3 h Hot extraction: toluene Ir₂(L43) L43

54% Ir₂(L43) 260° C.; 3 h Hot extraction: butyl acetate Ir₂(L44) L44

50% Ir₂(L44) 260° C.; 3 h Hot extraction: ethyl acetate Ir₂(L45) L45

57% Ir₂(L45) 260° C.; 3 h Hot extraction: ethyl acetate Rh- Ir(L1) L1 Rh(acac)₃ Ir(acac)₃

48% Rh-Ir(L1) 250° C.; 2 h Hot extraction: toluene Rh- Ir(L17) L17 Rh(acac)₃ Ir(acac)₃

45% Rh-Ir(L17) 260° C.; 3 h Hot extraction: toluene Variant B - Carbene complexes Ir₂(L120) LV120

22% Ir₂(L121) LV121

25% Ir₂(L122) LV122

23% Ir₂(L123) LV123

27% Ir₂(L130) LV130

24% Ir₂(L131) LV131

20% Ir₂(L132) LV132

26% Ir₂(L133) LV133

28% D: Functionalization of the Metal Complexes: 1) Halogenation of the Iridium Complexes:

To a solution or suspension of 10 mmol of a complex bearing A×C—H groups (with A=1-4) in the para position to the iridium in the bidentate sub-ligand in 500 to 2000 ml of dichloromethane according to the solubility of the metal complexes is added, in the dark and with exclusion of air, at −30 to +30° C., A×10.5 mmol of N-halosuccinimide (halogen: Cl, Br, I), and the mixture is stirred for 20 h. Complexes of sparing solubility in DCM may also be converted in other solvents (TCE, THF, DMF, chlorobenzene, etc.) and at elevated temperature. Subsequently, the solvent is substantially removed under reduced pressure. The residue is extracted by boiling with 100 ml of methanol, and the solids are filtered off with suction, washed three times with 30 ml of methanol and then dried under reduced pressure. This gives the iridium complexes brominated/halogenated in the para position to the iridium. Complexes having a HOMO (CV) of about −5.1 to −5.0 eV and of smaller magnitude have a tendency to oxidation (Ir(III)→Ir(IV)), the oxidizing agent being bromine released from NBS. This oxidation reaction is apparent by a distinct green hue or brown hue in the otherwise yellow to red solutions/suspensions of the emitters. In such cases, 1-2 further equivalents of NBS are added. For workup, 300-500 ml of methanol and 4 ml of hydrazine hydrate as reducing agent are added, which causes the green or brown solutions/suspensions to turn yellow or red (reduction of Ir(IV)→Ir(III)). Then the solvent is substantially drawn off under reduced pressure, 300 ml of methanol are added, and the solids are filtered off with suction, washed three times with 100 ml each time of methanol and dried under reduced pressure.

Substoichiometric brominations, for example mono- and dibrominations, of complexes having 4 C—H groups in the para position to the iridium atoms usually proceed less selectively than the stoichiometric brominations. The crude products of these brominations can be separated by chromatography (CombiFlash Torrent from A. Semrau).

Synthesis of Ir₂(L1-4Br):

To a suspension of 16.8 g (10 mmol) of Ir₂(L1) in 2000 ml of DCM are added 5.0 g (45 mmol) of N-bromosuccinimide all at once and then the mixture is stirred for 20 h. 2 ml of hydrazine hydrate and then 300 ml of MeOH are added. After removing about 1900 ml of the DCM under reduced pressure, the red solids are filtered off with suction, washed three times with about 50 ml of methanol and dried under reduced pressure. Yield: 18.5 g (9.3 mmol), 93%; purity: >99.0% by NMR.

The following compounds can be synthesized in an analogous manner:

Ex. Reactant Product/amount of NBS Yield Rh₂(L1-4Br) Rh₂(L1)

90% Ir₂(L2-4Br) Ir₂(L2)

95% Rh₂(L2-4Br) Rh₂(L2) Rh₂(L2-4Br) 88% 4.5 equiv. NBS Ir₂(L3-4Br) Ir₂(L3) Ir₂(L3-4Br) 96% 4.5 equiv. NBS Ir₂(L4-4Br) Ir₂(L4) Ir₂(L4-4Br) 92% 4.5 equiv. NBS Ir₂(L5-4Br) Ir₂(L5) Ir₂(L5-4Br) 84% 5 equiv. NBS Ir₂(L6-4Br) Ir₂(L6) Ir₂(L6-4Br) 95% 5 equiv NBS; 0.01 equiv HBr (aq) Ir₂(L8-4Br) Ir₂(L8) Ir₂(L8-4Br) 83% 5 equiv. NBS Ir₂(L9-4Br) Ir₂(L9) Ir₂(L9-4Br) 87% 4.5 equiv. NBS Ir₂(L10-4Br) Ir₂(L10) Ir₂(L10-4Br) 88% 5 equiv. NBS Ir₂(L11-4Br) Ir₂(L11) I1-Ir₂(L11-4Br) 91% 4.5 equiv. NBS Ir₂(L12-4Br) Ir₂(L12) Ir₂(L12-4Br) 92% 4.5 equiv. NBS Ir₂(L13-4Br) Ir₂(L13) Ir₂(L13-4Br) 94% 4.5 equiv. NBS Ir₂(L14-4Br) Ir₂(L14) Ir₂(L14-4Br) 90% 5 equiv. NBS, 0.02 equiv. HBr (aq) Ir₂(L15-4Br) Ir₂(L15)

92% Ir₂(L16-4Br) Ir₂(L16)

86% Ir₂(L18-4Br) Ir₂(L18) Ir₂(L18-4Br) 81% 5 equiv. NBS Ir₂(L21-4Br) Ir₂(L21) Ir₂(L21-4Br) 95% 4.5 equiv. NBS Ir₂(L23-4Br) Ir₂(L23) Ir₂(L23-4Br) 83% 5 equiv. NBS Ir₂(L26-4Br) Ir₂(L26)

90% Ir₂(L27-4Br) Ir₂(L27)

95% Ir₂(L31-4Br) Ir₂(L31)

86% L32(L32-4Br) Ir₂(L32) Ir₂(L32-4Br) 91% 4.5 equiv. NBS: Ir₂(L33-4Br) Ir₂(L33)

90% Ir₂(L34-4Br) Ir₂(L34) Ir₂(L34-4Br) 85% 4.5 equiv. NBS Ir₂(L35-4Br) Ir₂(L35)

89% Ir₂(L36-4-Br) Ir₂(L36)

84% Ir₂(L39-4Br) Ir₂(L39)

88% Ir₂(L120-4Br) Ir₂(L120)

90% Ir₂(L131-4Br) Ir₂(L131)

87% 2) Suzuki Coupling with the Brominated Iridium Complexes: Variant a, Biphasic Reaction Mixture:

To a suspension of 10 mmol of a brominated complex, 12-20 mmol of boronic acid or boronic ester per Br function and 60-100 mmol of tripotassium phosphate in a mixture of 300 ml of toluene, 100 ml of dioxane and 300 ml of water are added 0.6 mmol of tri-o-tolylphosphine and then 0.1 mmol of palladium(II) acetate, and the mixture is heated under reflux for 16 h. After cooling, 500 ml of water and 200 ml of toluene are added, the aqueous phase is removed, and the organic phase is washed three times with 200 ml of water and once with 200 ml of saturated sodium chloride solution and dried over magnesium sulfate. The mixture is filtered through a Celite bed and washed through with toluene, the toluene is removed almost completely under reduced pressure, 300 ml of methanol are added, and the precipitated crude product is filtered off with suction, washed three times with 50 ml each time of methanol and dried under reduced pressure. The crude product is chromatographed on silica gel in an automated column system (Torrent from Semrau). Subsequently, the complex is purified further by hot extraction in solvents such as ethyl acetate, toluene, dioxane, acetonitrile, cyclohexane, ortho- or para-xylene, n-butyl acetate etc. Alternatively, it is possible to recrystallize from these solvents and high boilers such as dimethylformamide, dimethyl sulfoxide or mesitylene. The metal complex is finally heat-treated. The heat treatment is effected under high vacuum (p about 10⁻⁶ mbar) within the temperature range of about 200-350° C.

Variant B, Monophasic Reaction Mixture:

To a suspension of 10 mmol of a brominated complex, 12-20 mmol of boronic acid or boronic ester per Br function and 100-180 mmol of the base (potassium fluoride, tripotassium phosphate (anhydrous, monohydrate or trihydrate), potassium carbonate, cesium carbonate etc.) and 100 g of glass beads (diameter 3 mm) in 100 ml-500 ml of an aprotic solvent (THF, dioxane, xylene, mesitylene, dimethylacetamide, NMP, DMSO, etc.) is added 0.2 mmol of tetrakis(triphenylphosphine)palladium(0) [14221-01-3], and the mixture is heated under reflux for 24 h. Alternatively, it is possible to use other phosphines such as triphenylphosphine, tri-tert-butylphosphine, SPhos, XPhos, RuPhos, XanthPhos, etc. in combination with Pd(OAc)₂, the preferred phosphine:palladium ratio in the case of these phosphines being 3:1 to 1.2:1. The solvent is removed under reduced pressure, the product is taken up in a suitable solvent (toluene, dichloromethane, ethyl acetate, etc.) and purification is effected as described in Variant A.

Synthesis of Ir₂100:

Variant B:

Use of 19.92 g (10.0 mmol) of Ir(L1-4Br) and 25.3 g (80.0 mmol) of 2-(3,5-di-tert-butylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane [1071924-13-4], 27.6 g (120 mmol) of tripotassium phosphate monohydrate, 116 mg (0.1 mmol) of tetrakis(triphenylphosphine)palladium(0), 500 ml of dry dimethyl sulfoxide, 100° C., 16 h. Chromatographic separation on silica gel with toluene/heptane (automated column system, Torrent from Axel Semrau), followed by hot extraction five times with ethyl acetate. Yield: 13.6 g (5.6 mmol), 56%; purity: about 99.9% by HPLC.

In an analogous manner, it is possible to prepare the following compounds:

Reactant Variant/Reaction conditions Ex. Boronic acid Product/hot extractant (HE) Yield Rh₂100

28% Ir₂101

53% Ir₂102

56% Ir₂103

48% Ir₂104

47% Ir₂105

21% Ir₂106

51% Ir₂107

52% Ir₂108

50% Ir₂109

45% Ir₂110

48% Ir₂111

54% Ir₂112

47% Ir₂113

51% 3) Deuteration of Ir Complexes: Example: Ir₂(L12-D12)

A mixture of 2.12 g (1 mmol) of Ir₂(L12), 68 mg (1 mmol) of sodium ethoxide, 5 ml of methanol-D4 and 80 ml of DMSO-D6 is heated to 120° C. for 2 h. After cooling to 50° C., 1 ml of DCI (10% aqueous solution) is added. The solvent is removed under reduced pressure and the residue is chromatographed with DCM on silica gel. Yield: 2.11 g (0.95 mmol), 95%, deuteration level >95%.

In an analogous manner, it is possible to prepare the following compounds:

Ex. Reactant/product Yield Ir₂(L17-D12)

90%

Example: Photophysical Properties of Ir₂(L1)

The maximum in the photoluminescence spectrum in nm is determined in a degassed about 10⁻⁵ molar solution of Ir₂(L1) in toluene at room temperature at an excitation wavelength of 400 nm. The photoluminescence maximum is at 603 nm.

Device Examples Example 1: Production of the OLEDs

The complexes of the invention can be processed from solution and lead, compared to vacuum-processed OLEDs, to much more easily producible OLEDs having properties that are nevertheless good. There are already many descriptions of the production of completely solution-based OLEDs in the literature, for example in WO 2004/037887. There have likewise been many descriptions of the production of vacuum-based OLEDs, including in WO 2004/058911. In the examples discussed hereinafter, layers applied in a solution-based and vacuum-based manner are combined within an OLED, and so the processing up to and including the emission layer is effected from solution and in the subsequent layers (hole blocker layer and electron transport layer) from vacuum. For this purpose, the previously described general methods are matched to the circumstances described here (layer thickness variation, materials) and combined as follows. The general structure is as follows: substrate/ITO (50 nm)/hole injection layer (HIL)/hole transport layer (HTL)/emission layer (EML)/hole blocker layer (HBL)/electron transport layer (ETL)/cathode (aluminum, 100 nm). Substrates used are glass plates coated with structured ITO (indium tin oxide) of thickness 50 nm. For better processing, they are coated with PEDOT:PSS (poly(3,4-ethylenedioxy-2,5-thiophene) polystyrenesulfonate, purchased from Heraeus Precious Metals GmbH & Co. KG, Germany). PEDOT:PSS is spun on from water under air and subsequently baked under air at 180° C. for 10 minutes in order to remove residual water. The hole transport layer and the emission layer are applied to these coated glass plates. The hole transport layer used is crosslinkable. A polymer of the structure shown below is used, which can be synthesized according to WO 2010/097155 or WO 2013/156130:

The hole transport polymer is dissolved in toluene. The typical solids content of such solutions is about 5 g/I when, as here, the layer thickness of 20 nm which is typical of a device is to be achieved by means of spin-coating. The layers are spun on in an inert gas atmosphere, argon in the present case, and baked at 180° C. for 60 minutes.

The emission layer is always composed of at least one matrix material (host material) and an emitting dopant (emitter). In addition, mixtures of a plurality of matrix materials and co-dopants may occur. Details given in such a form as TMM-A (92%):dopant (8%) mean here that the material TMM-A is present in the emission layer in a proportion by weight of 92% and dopant in a proportion by weight of 8%. The mixture for the emission layer is dissolved in toluene or optionally chlorobenzene. The typical solids content of such solutions is about 17 g/I when, as here, the layer thickness of 60 nm which is typical of a device is to be achieved by means of spin-coating. The layers are spun on in an inert gas atmosphere, argon in the present case, and baked at 150° C. for 10 minutes. The materials used in the present case are shown in table 1.

TABLE 1 EML materials used

The materials for the hole blocker layer and electron transport layer are applied by thermal vapor deposition in a vacuum chamber. The electron transport layer, for example, may consist of more than one material, the materials being added to one another by co-evaporation in a particular proportion by volume. Details given in such a form as ETM1:ETM2 (50%:50%) mean here that the ETM1 and ETM2 materials are present in the layer in a proportion by volume of 50% each. The materials used in the present case are shown in table 2.

TABLE 2 HBL and ETL materials used

The cathode is formed by the thermal evaporation of a 100 nm aluminum layer. The OLEDs are characterized in a standard manner. The EML mixtures and structures of the OLED components examined are shown in table 3 and table 4. In all cases, intense yellow through orange-red to red emission is observed.

TABLE 3 EML mixtures of the OLED components examined Matrix A Co-matrix B Co-dopant C Dopant D Ex. material % material % material % material % E-1  A-1 30 B-1 34 C-1 30 Ir₂(L1) 6 E-2  A-1 50 B-1 25 C-1 15 Ir₂(L1) 10 E-3  A-1 40 B-1 45 — — Ir₂(L1) 15 E-4  A-1 50 B-1 25 C-1 15 Rh₂(L1) 10 E-5  A-1 50 B-1 25 C-1 15 Ir₂(L2) 10 E-6  A-1 50 B-1 25 C-1 15 Rh₂(L2) 10 E-7  A-1 50 B-1 25 C-1 15 Ir₂(L3) 10 E-8  A-1 50 B-1 25 C-1 15 Ir₂(L4) 10 E-9  A-1 50 B-1 25 C-1 15 Ir₂(L5) 10 E-10 A-1 50 B-1 25 C-1 15 Ir₂(L6) 10 E-11 A-1 50 B-1 25 C-1 15 Ir₂(L7) 10 E-12 A-1 50 B-1 25 C-1 15 Ir₂(L8) 10 E-13 A-1 50 B-1 25 C-1 15 Ir₂(L9) 10 E-14 A-1 50 B-1 25 C-1 15 Ir₂(L10) 10 E-15 A-1 50 B-1 25 C-1 15 Ir₂(L11) 10 E-16 A-1 50 B-1 25 C-1 15 Ir₂(L12) 10 E-17 A-1 50 B-1 25 C-1 15 Ir₂(L13) 10 E-18 A-1 50 B-1 25 C-1 15 Ir₂(L14) 10 E-19 A-1 50 B-1 25 C-1 15 Ir₂(L15) 10 E-20 A-1 50 B-1 25 C-1 15 Ir₂(L16) 10 E-21 A-1 50 B-1 25 C-1 15 Ir₂(L17) 10 E-22 A-1 50 B-1 25 C-1 15 Ir₂(L18) 10 E-23 A-1 50 B-1 25 C-1 15 Ir₂(L19) 10 E-24 A-1 50 B-1 25 C-1 15 Ir₂(L20) 10 E-25 A-1 50 B-1 25 C-1 15 Ir₂(L21) 10 E-26 A-1 50 B-1 25 C-1 15 Ir₂(L22) 10 E-27 A-1 50 B-1 25 C-1 15 Ir₂(L23) 10 E-28 A-1 50 B-1 25 C-1 15 Ir₂(L24) 10 E-29 A-1 50 B-1 25 C-1 15 Ir₂(L25) 10 E-30 A-1 50 B-1 25 C-1 15 Ir₂(L26) 10 E-31 A-1 50 B-1 25 C-1 15 Ir₂(L27) 10 E-32 A-1 50 B-1 25 C-1 15 Ir₂(L28) 10 E-33 A-1 50 B-1 25 C-1 15 Ir₂(L29) 10 E-34 A-1 50 B-1 25 C-1 15 Ir₂(L30) 10 E-35 A-1 50 B-1 25 C-1 15 Ir₂(L31) 10 E-36 A-1 50 B-1 25 C-1 15 Ir₂(L32) 10 E-37 A-1 50 B-1 25 C-1 15 Ir₂(L33) 10 E-38 A-1 50 B-1 25 C-1 15 Ir₂(L34) 10 E-39 A-1 50 B-1 25 C-1 15 Ir₂(L35) 10 E-40 A-1 50 B-1 25 C-1 15 Ir₂(L36) 10 E-41 A-1 50 B-1 25 C-1 15 Ir₂(L37) 10 E-42 A-1 50 B-1 25 C-1 15 Ir₂(L38) 10 E-43 A-1 50 B-1 25 C-1 15 Ir₂(L39) 10 E-44 A-1 50 B-1 25 C-1 15 Ir₂(L40) 10 E-45 A-1 50 B-1 25 C-1 15 Ir₂(L41) 10 E-46 A-1 50 B-1 25 C-1 15 Ir₂(L42) 10 E-47 A-1 50 B-1 25 C-1 15 Ir₂(L43) 10 E-48 A-1 50 B-1 25 C-1 15 Ir₂(L44) 10 E-49 A-1 50 B-1 25 C-1 15 Ir₂(L45) 10 E-50 A-1 50 B-1 25 C-1 15 Rh—Ir(L1) 10 E-51 A-1 50 B-1 25 C-1 15 Rh—Ir(L17) 10 E-52 A-1 50 B-1 25 C-1 15 Ir₂(L120) 10 E-53 A-1 50 B-1 25 C-1 15 Ir₂(L121) 10 E-54 A-1 50 B-1 25 C-1 15 Ir₂(L122) 10 E-55 A-1 50 B-1 25 C-1 15 Ir₂(L123) 10 E-56 A-1 50 B-1 25 C-1 15 Ir₂(L130) 10 E-57 A-1 50 B-1 25 C-1 15 Ir₂(L131) 10 E-58 A-1 50 B-1 25 C-1 15 Ir₂(L132) 10 E-59 A-1 50 B-1 25 C-1 15 Ir₂(L133) 10 E-60 A-1 50 B-1 25 C-1 15 Ir₂100 10 E-61 A-1 50 B-1 25 C-1 15 Rh₂100 10 E-62 A-1 50 B-1 25 C-1 15 Ir₂101 10 E-63 A-1 50 B-1 25 C-1 15 Ir₂102 10 E-64 A-1 50 B-1 25 C-1 15 Ir₂103 10 E-65 A-1 50 B-1 25 C-1 15 Ir₂104 10 E-66 A-1 50 B-1 25 C-1 15 Ir₂105 10 E-67 A-1 50 B-1 25 C-1 15 Ir₂106 10 E-68 A-1 50 B-1 25 C-1 15 Ir₂107 10 E-69 A-1 50 B-1 25 C-1 15 Ir₂108 10 E-70 A-1 50 B-1 25 C-1 15 Ir₂109 10 E-71 A-1 50 B-1 25 C-1 15 Ir₂110 10 E-72 A-1 50 B-1 25 C-1 15 Ir₂111 10 E-73 A-1 50 B-1 25 C-1 15 Ir₂112 10 E-74 A-1 50 B-1 25 C-1 15 Ir₂113 10 E-75 A-1 50 B-1 25 C-1 15 Ir₂(L12-D12) 10 E-76 A-1 50 B-1 25 C-1 15 Ir₂(L17-D12) 10

TABLE 4 Structure of the OLED components examined HTL EML HBL HIL (thick- (thick- (thick- ETL Ex. (thickness) ness) ness) ness) (thickness) E-1 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (60 nm) E-2 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-3 PEDOT HTL2 70 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-4 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-5 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-6 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-7 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-8 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-9 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-10 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-11 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-12 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-13 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-14 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-15 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-16 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-17 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-18 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-19 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-20 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-21 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-22 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-23 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-24 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-25 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-26 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-27 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-28 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-29 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-30 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-31 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-32 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-33 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-34 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-35 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-36 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-37 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-38 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-39 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-40 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-41 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-42 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-43 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-44 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-45 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-46 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-47 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-48 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-49 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-50 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-51 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-52 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-53 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-54 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-55 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-56 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-57 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-58 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-59 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-60 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-61 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-62 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-63 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-64 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-65 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-66 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-67 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-68 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-69 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-70 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-71 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-72 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-73 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-74 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-75 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) E-76 PEDOT HTL2 60 nm ETM-1 ETM-1(50%):ETM-2 (60 nm) (20 nm) (10 nm) (50%) (40 nm) 

The invention claimed is:
 1. A compound of formula (1):

wherein M is the same or different in each instance and is iridium or rhodium; D is the same or different in each instance and is C or N; X is the same or different in each instance and is CR or N; or two adjacent X together in the cycle containing E are CR or N and the third X is CR or N when either one D in the cycle coordinates as an anionic nitrogen atom to M or when E is N; E is C or N, wherein E can be N only when two adjacent X together in the cycle containing E are CR or N and the third X is CR or N; V is the same or different at each instance and is a group of the formula (2) or (3)

wherein the dotted bond bonded directly to the cycle is the bond to the corresponding 6-membered aryl or heteroaryl group of formula (1) and the two dotted bonds to A are each the bonds to the sub-ligands L; L is the same or different in each instance and is a bidentate monoanionic sub-ligand; X¹ is the same or different in each instance and is CR or N; X² is the same or different in each instance and is CR or N; or two adjacent X² groups together are NR, O, or S, so as to define a five-membered ring, and the remaining X² are the same or different in each instance and are CR or N; or two adjacent X² groups together are CR or N when one of the X³ groups in the cycle is N, so as to define a five-membered ring; with the proviso that not more than two adjacent X² groups are N; X³ is C in each instance or one X³ group is N and the other X³ groups in the same cycle are C; with the proviso that two adjacent X² groups together are CR or N when one of the X³ groups in the cycle is N; A¹ is the same or different in each instance and is C(R)₂ or O; A² is the same or different in each instance and is CR, P(═O), B, or SiR, with the proviso that, when A² is P, (═O), or SiR, A¹ is O and the A bonded to the A² is not —C(═O)—NR′— or —C(═O)—O—; A is the same or different in each instance and is —CR═CR—, —C(═O)—NR′—, —C(═O)—O—,—CR₂—CR₂—, —CR₂—O—, or a group of formula (4):

wherein the dotted bond is the position of the bond of a bidentate sub-ligand L to the group of formula (4) and * is the position of the linkage of the group of formula (4) to the central cyclic group; R is the same or different in each instance and is H, D, F, Cl, Br, I, N(R¹)₂, CN, NO₂, OR¹, SR¹, COOH, C(═O)N(R¹)₂, Si(R¹)₃, B(OR¹)₂, C(═O)R¹, P(═O)(R¹)₂, S(═O)R¹, S(═O)₂R¹, OSO₂R¹, COO(cation), SO₃(cation), OSO₃(cation), OPO₃ (cation)₂, O(cation), N(R¹)₃(anion), P(R¹)₃(anion), a straight-chain alkyl group having 1 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, wherein the alkyl, alkenyl, or alkynyl group is in each case optionally substituted by one or more radicals R¹ and wherein one or more nonadjacent CH₂ groups are optionally replaced by Si(R¹)₂, C═O, NR¹, O, S, or CONR¹, or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms and which is optionally substituted in each case by one or more radicals R¹; and wherein two radicals R together optionally define a ring system; R′ is the same or different in each instance and is H, D, a straight-chain alkyl group having 1 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, wherein the alkyl group is in each case optionally substituted by one or more radicals R¹ and wherein one or more nonadjacent CH₂ groups are optionally replaced by Si(R¹)₂, or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms and which is optionally substituted in each case by one or more radicals R¹; R¹ is the same or different in each instance and is H, D, F, Cl, Br, I, N(R²)₂, CN, NO₂, OR², SR², Si(R²)₃, B(OR²)₂, C(═O)R², P(═O)(R²)₂, S(═O)R², S(═O)₂R², OSO₂R², COO(cation), SO₃(cation), OSO₃ (cation), OPO₃ (cation)₂, O(cation), N(R²)₃(anion), P(R²)₃(anion), a straight-chain alkyl group having 1 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, wherein the alkyl, alkenyl, or alkynyl group is in each case optionally substituted by one or more radicals R², and wherein one or more nonadjacent CH₂ groups are optionally replaced by Si(R²)₂, C═O, NR², O, S, or CONR², or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms and which are optionally substituted in each case by one or more radicals R²; and wherein two or more radicals R¹ together optionally define a ring system; R² is the same or different in each instance and is H, D, F, or an aliphatic, aromatic, or heteroaromatic organic radical having 1 to 20 carbon atoms, wherein one or more hydrogen atoms is also optionally replaced by F; cation is the same or different in each instance and is selected from the group consisting of proton, deuteron, alkali metal ions, alkaline earth metal ions, ammonium, tetraalkylammonium, and tetraalkylphosphonium; anion is the same or different in each instance and is selected from the group consisting of halides, carboxylates R²—COO⁻, cyanide, cyanate, isocyanate, thiocyanate, thioisocyanate, hydroxide, BF₄ ⁻, PF₆ ⁻, B(C₆F₅)₄—, carbonate, and sulfonates.
 2. The compound of claim 1, wherein both metals M are Ir(III) and the compound is an uncharged compound.
 3. The compound of claim 1, wherein the compound is selected from the group consisting of compounds of formulae (1′), (1″), and (1″):

wherein the radicals R in the position ortho to the groups D and in the position ortho to the coordinating nitrogen atom in formula (1″) are each the same or different in each instance and are selected from the group consisting of H, D, F, CH₃, and CD₃.
 4. The compound of claim 1, wherein the compound is selected from the group consisting of compounds of formulae (1a) through (1h):

wherein X in the five-membered ling of formulae (1d) through (1h) is the same or different in each instance and is CR or N.
 5. The compound of claim 1, wherein the compound is selected from the group consisting of compounds of formulae (1a′) through (1h′):

wherein the radicals R in position ortho to the coordinating carbon or nitrogen atoms are each the same or different in each instance and are selected from the group consisting of H, D, F, CH₃, and CD₃.
 6. The compound of claim 1, wherein the group of formula (2) is selected from the group consisting of structures of formulae (5) through (8) and the group of formula (3) is selected from the group consisting of structures of formulae (9) through (13):


7. The compound of claim 1, wherein the group of formula (2) has a structure of the formula (5′) and the group of the formula (3) has a structure of the formula (9′) or (9″)


8. The compound of claim 1, wherein A is the same or different in each instance and is selected from the group consisting of —C(═O)—O—, —C(═O)—NR′—, or a group of formula (4), wherein the group of formula (4) is selected from the group consisting of structures of formulae (14) through (38):


9. The compound of claim 1, wherein the group of formula (2) is selected from the group consisting of structures of formulae (2a) through (2i) and the group of formula (3) is selected from the group consisting of structures of formulae (3a) through (3i):


10. The compound of claim 1, wherein V is selected from the group consisting of structures of formulae (5a″) and (5a′″):


11. The compound of claim 1, wherein the bidentate sub-ligands L are the same or different in each instance and are selected from the group consisting of structures of formulae (L-1), (L-2), and (L-3):

wherein the dotted bond is the bond of sub-ligand L to the group of formulae (2) or (3); CyC is the same or different in each instance and is a substituted or unsubstituted aryl or heteroaryl group having 5 to 14 aromatic ring atoms and coordinates to M via a carbon atom and is bonded to CyD via a covalent bond; CyD is the same or different in each instance and is a substituted or unsubstituted heteroaryl group having 5 to 14 aromatic ring atoms and coordinates to M via a nitrogen atom or via a carbene carbon atom and is bonded to CyC via a covalent bond; and wherein two or more of the optional substituents together optionally define a ring system.
 12. A process for preparing the compound of claim 1 comprising reacting the ligand with metal alkoxides of formula (57), with metal ketoketonates of formula (58), with metal halides of formula (59), or with metal carboxylates of formula (60):

wherein Hal is F, Cl, Br, or I; the iridium or rhodium reactants are optionally in the form of the corresponding hydrates and/or iridium or rhodium compounds that bear both alkoxide and/or halide and/or hydroxyl; and wherein ketoketonate radicals are also optionally employed.
 13. A formulation comprising at least one compound of claim 1 and at least one solvent.
 14. An electronic device comprising at least one compound of claim
 1. 15. The electronic device of claim 14, wherein the electronic device is an organic electroluminescent device and wherein the compound of formula (1) is present in the electroluminescent device as an emitting compound in one or more emitting layers. 